Yes you can file for defamation if the said allegations are not proved. 

As per the Hindu Marriage Act impotency is a valid ground for seeking divorce. If your wife files the case against you, you will be ordered by the court for the medical examination. If the allegation is right it will be reflected in the judgement as well. 

Court can draw adverse inference that you are impotent as you refused to undergo medical tests 

2) she can file case of cheating against you 

3) she can also claim alimony but if there is no substantial differences in your income she would not get alimony 

4) she would not be entitled to marriage expenses 

1. if you are not impotent, you should contest the case,

2. if you both want divorce, go for mutual consent divorce, not annulment

3. annulment will have a negative impact on you, both legally and socially,

4. you have to pay the alimony, 

“amount of MAINTENANCE/ALIMONY depends on various factors such as Living Standard, Financial Status, Properties held, assets, responsibilities, custody of children, expenses on marriage etc, therefore, without going through deeply with facts its really unfair to tell an amount. a detailed personal discussion will enable me to answer this promptly"

more alimony in annulment

Dear Sir,

My answers are as follows:

1. In actual cases happened in past..what happens 8n such annulment of Marriage due to husband's impotency happens if the husband looses the case if he denies to go under a medical check up instructed by court ( because he/I also want the annulment to happen and I don't want winning the case). By "what happens" I want to know about concequesnces; in the same case or in farther future cases that the wife can file based on the verdict of this case.

Like cheating case, ant other (unknown to me) criminal cases)

Ans: The only consequence is that it will be on public record that you are impotent if you allow the divorce petition is filed by your wife is allowed.   

2. She will not be eligible for maintenance or alimony I know. Will she be able to get damage recovery claims for the marriage cost stating the Marriage was annuled due to husband's impotency and due to that can the claim any random amount like 15-20 lacs without any proof or justification like producing marriage expanses etc?

Ans: It is a non disclosure of your marital condition amounting to mental torture and other lowering of status in the life of your wife as such Court may award compensation to her if you do not effectively conduct above case. You may have an option to approach Supreme Court for transfer of above case as last residence of both of you seems to be Bengaluru. Further you have an option to file counter divorce application on your own allegations against your wife.

you should contest case of anullment filed by wife . 

2) if you do not contest wife would get decree of annulment on account of your impotency 

3) it would affect your second marriage prospects 

4) further she can claim compensation from you . also file case of cheating against you 

5) file for contested divorce 

Filling false cases ground of divorce, refute her allegations and file cross claim in same case with the prayer to grant divorce but on your grounds instead of impotency. You if agreed with impotency, than you will be liable to pay maintenance, marriages expanses etc.

It's better you settle the matter and file consent divorce if not contesting is last option

- Your wife has filed the case of annulment after accusing you for impotency,hence she will have to prove the same .

- Further, if the said allegation will be proved ,then it will become a ground for divorce automatically as per law.

- Since, she is working lady and getting same salary like you, hence she will not get any maintenance from you.

- If, she is not ready for mutually divorce without condition of hefty amount payment , then there is no solution except contesting the case.

If you are not impotent or you are medically fit and your wife putting false allegation on record or if you proved then you filled defamation case and cruelty case against you wife. 

Dear Sir,

You can make use of the following judgment:

Calling a man impotent amounts to defaming him, says Bombay high court

Referring somebody as an “impotent person” reflects badly on his manhood and prima facie amounts to defamation, the Bombay high court said and refused to quash criminal proceedings against a resident of Andhra Pradesh by her estranged husband for terming him ‘impotent’.

She cannot file any criminal case after verdict of annulement case. 

Yes she can claim marriage expenses from husband but she have to give proof of those expenses.

1.  She has filed the annulment case which has been decreed on merits or if may be decreed in your absence if you choose to not to attend the case.

However your marriage shall be annulled but there is no reason nor there is provision in law for her to follow it up with a cheating case.

She may not be able to do it, in fact she may not even think of following it up with any further litigation against you once she is freed from your bindings.

She may not be able to claim compensation also since she only opted for annulment.

Since she wa the person who deserted you without any valid reason you can cite that as a reason to deny her the alimony amount in the event of the contested divorce.

You don't  be behind such imaginary concepts alone.

You may concentrate on what is to be done now and then plan for the future program as per the circumstances.

Dear Sir, 

The following information may kindly be read:

Can't say husband impotent without proof: Gujarat high court

Rajendra Dalal had challenged a family court's order granting divorce to his wife Dharmishta on the ground of impotency and cruelty, in the Gujarat High Court. A division bench of Justice Jayant Patel and Abhilasha Kumari, last week, rejected the man's appeal, saying that the petition was devoid of merits.

The court, however, observed that there was no conclusive evidence to prove that the man was impotent or the marriage was not consummated. "The finding of the Family Court on this point, therefore, cannot be endorsed," it observed. It said the decree of dissolution of marriage has been passed by the family court under provisions of Section 13(1) of the Hindu Marriage Act, on  ground of cruelty and desertion and not under Section 12 (impotency).

Also, the family court, while granting divorce had recorded cogent findings on the ground of desertion and cruelty against the man, the court added.In view of the material on record that the man used to harass his wife at her work place and misbehave with her, the permanent injunction granted by the family court restraining the appellant from harassing her at work place and misbehaving with her was justified, the court observed before dismissing the petition.

The woman had got divorce from the man from a family court on the grounds that he was impotent and could not consummate the marriage. She had also claimed mental and physical torture on husband's side. The couple had married in 2000. The man worked with a private firm, while the woman had a government job.

The woman initiated divorce proceedings in 2003 where she claimed that she was frustrated because her marriage not being consummated, and also due to harassment by her husband. In 2009, the family court passed the orders in favour the woman and held that she was entitled for divorce on grounds of cruelty and impotency.