Theresa May has warned Conservative MPs not to scupper a backbench SNP bill on domestic violence.

The House of Commons will debate the Private Member's Bill, which aims to force the UK to finally ratify an international convention on violence against women, later this week.

Britain signed up to the Istanbul Convention in June 2012 but had so far failed to ratify it, despite repeated calls from campaigners and opposition MPs.

The Conservative Government is backing the SNP's PMB.

But Tory MPs tried to "talk out" the Bill the last time it came before the Commons.

Under pressure from the SNP's Westminster leader Angus Robertson, Mrs May urged her own backbenchers not to attempt to derail the Bill.

At Prime Minister's Questions (PMQs), Mr Robertson called on the Prime Minister to show her commitment to ending violence against women and ratify the convention "as a priority".

He added: "This Friday the House of Commons will consider a Bill on the Istanbul Convention, and we know that Government ministers have been working very hard with my colleague, the member for Banff and Buchan who has cross-party support for her Bill.

"So given the importance of this issue and the Prime Minister's personal commitment that she has outlined again today, will she join me in encouraging members to support the Bill, and discourage any attempt to use parliamentary wrecking tactics to stop it?"

Mrs May said that she was "very happy" to encourage MPs to back the Bill.

She added that ministers had tabled mutually agreed amendments to the Bill and said: "I hope that all honourable friends who will be here on Friday will be supporting those measures.

"This is an important Bill."

Mr Robertson said that he welcomed the Prime Minister’s support.

Mrs May, who has a Commons majority of just 12, has struggled at times to control her backbenchers, leading to claims they are the 'real opposition'.

Tory MP Philip Davies talked for more than an hour in an attempt to prevent the passage of the bill, brought by the SNP's Eilidh Whiteford, the MP for Banff and Buchan, when it was last debated in December.

He called the bill "sexist against men" and "discriminatory".

He added that the Bill was "pointless and wrong" because "not all victims are female and not all offenders are male".

After he finished speaking, Labour MP Thangam Debbonaire declared: "That is 78 minutes I believe I’m never going to get back".

Mr Davies has previously campaigned for parliament to recognise International Men's Day and criticised "militant feminists".

Harry Potter star Emma Watson has contacted all MPs and urged them to attend the debate.

The bill faces a race against time to become law before the end of the current parliamentary session.