SNP MPs will today join a mass rally of EU nationals outside Westminster as a campaign to protect their status intensifies.

Joanna Cherry, the party’s justice and home affairs spokeswoman, will renew calls for Theresa May to guarantee their residency and rights.

The UK Government has refused to do so repeatedly in the nine months since the EU referendum and, this month, Tory MPs voted down such an amendment to the Brexit Bill. An estimated 3.3 million EU nationals live in the UK and evidence suggests they make a substantial contribution to the economy.

“EU nationals who live, work and study in the UK make a huge and valued contribution that benefits the whole country,” said Cherry.

“It is unacceptable that, almost nine months since the EU referendum, Tory ministers continue to leave these families in limbo by treating them as bargaining chips.”

The mass lobby of parliament is taking place as part of the #1DayWithoutUs national day of action.

Labour’s Peter Mandelson added his voice to the issue yesterday, warning the Government that there is a “strong body of opinion” among peers over guaranteeing the future of EU nationals.

The former EU commissioner also cautioned against a “Brexit at all costs” as the Bill moves to the Lords.

“We’re going to have less trade, we’re going to be paying through the nose for it and, broadly speaking, we’re going to have the same number of immigrants coming to the country as well,” he said on the BBC’s Andrew Marr show.

“Is that a reasonable deal? Don’t you think the public will have something to say about that outcome when the negotiation ends? I think they will.”

He added: “There is no trade agreement in the world that will give us the same benefits in trade that we have now if we were to follow the Government’s Brexit at all costs negotiation.”

Today fellow peer Labour former Cabinet minister Peter Hain will seek to force major changes on the Bill demanding the UK remains in the single market and retains an open border between Northern Ireland and the Republic.

He is expected to attack May for failing to represent the 48 per cent who voted in favour of Remain and argue that her exit strategy could lead to a “Trump Brexit” that turns the UK into a low tax haven.

Lord Hain will say: “The truth is the country was split down the middle – and still is.

“If the Prime Minister were really acting in the national interest, she would be representing [Remainers] too. She would be pursuing a ‘one nation Brexit’ not a partisan hard, right wing Brexit.”

The former Northern Ireland Secretary will warn the peace process could unravel under Brexit and has tabled an amendment, backed by another former holder of the post, Lord Murphy of Torfaen, calling for the border to remain open.

He will insist: “A ‘one nation Brexit’ would also mean guaranteeing a completely open border between Northern Ireland and the Republic – no security checks, no controls, physical or electronic. Otherwise I believe the peace process could unravel, as indeed Bertie Ahern, the former Taoiseach and so important to the success of that process, has said.”

Lord Hain will also push for a vote on keeping Britain in the single market, warning that severing ties with its biggest trade market will have a “devastating” impact on the economy.

The peer, who has previously said he will vote against the European Union (Notification of Withdrawal) Bill, will argue a deal could be done to keep Britain in the single market that included restricting free movement rules to people who have jobs.

A Home Office spokesman said securing the status of EU nationals and British expats is a “priority”.