THERESA May is to press ahead with plans to meet Donald Trump despite an unprecedented wave of international demonstrations against the new US President over the weekend.

The organisers of the “Sisters Marches” said more than five million people united in protest at the inauguration of the billionaire businessman turned politician, who proclaimed he would put “America First.”

Outraged by Trump’s campaign rhetoric and behaviour towards women, activists spearheaded more than 600 marches in the United States and hundreds of sympathy rallies across South America, Canada, Asia, Europe and Australia.

The demonstrations also highlighted strong discontent over Trump’s comments and policy positions on a wide range of groups, including Mexican immigrants, Muslims, disabled people and environmentalists.

But May yesterday confirmed she would meet him in Washington DC on Friday, insisting she would tell him when she found his behaviour or statements “unacceptable”.

The Prime Minister has previously used the term “unacceptable” to describe Trump’s suggestion that his fame allowed him to “do anything” to women, such as “grabbing them by the pussy”.

In an interview yesterday, May said the “special relationship” between the UK and US would allow her to criticise Trump where she saw fit.

Asked if she would raise the controversial tycoon’s treatment of women at their meeting, she told BBC One’s Andrew Marr Show: “I have already said that some of the comments that Donald Trump has made in relation to women are unacceptable, some of those he himself has apologised for.

“When I sit down I think the biggest statement that will be made about the role of women is the fact that I will be there as a female Prime Minister, Prime Minister of the United Kingdom, directly taking to him about the interests that we share.”

The PM highlighted her “track record” in defending the interests of women, including moves to tackle modern slavery and domestic violence while Home Secretary.

She said she was proud to be the country's second female premier, adding: “I will be talking to Donald Trump about the issues that we share – about how we can build on the special relationship. It’s the special relationship that also enables us to say when we do find things unacceptable.” She added: “Whenever there is something that I find unacceptable I will say that to Donald Trump.”

She also insisted Trump was looking for “early” talks on a UK-US free trade deal despite his “America First” strategy sparking concerns he would not be willing to reach an agreement.

May has also spoken of reducing barriers to trade before a formal deal can be reached after Brexit, amid reports of potential moves to set up a “passporting” system for transatlantic banking.

And she defended Trump’s widely-criticised “America First” message. "If you think about it, any leader, any government, as we do here in the United Kingdom when we look at any issue, we ensure that we’re putting the UK’s interests and the interests of British people first," she said.

May also suggested her visit would be followed by a state visit by Trump to Britain this year, which would include an audience with the Queen and the pomp and pageantry of which the President seems so fond.

Responding, Jeremy Corbyn urged May to directly criticise Trump’s misogyny and his call for Muslims to be banned from the US, and urged caution on any further trade deal with him, warning it could be unfavourable to the UK The Labour leader told Sky News’s Sophy Ridge on Sunday: “The idea that Donald Trump is suddenly going to roll over and offer some trade deal with Britain that doesn’t have strings attached, like investor protection where American companies can come in and run parts of our health service and be protected in doing so – I think she needs to be extremely careful.”