THERESA May has vowed to deliver Brexit on time as she prepares to take “new ideas” into Brussels talks – but a senior Brexiteer says Tory backbenchers will not support backstop changes.

Steve Baker, deputy chairman of Jacob Rees-Mogg’s European Research Group, says there is “trouble ahead” for the Prime Minister.

The comment followed a Sunday Telegraph piece in which she stated she would seek an alternative, or time-limiting changes, to the Irish border backstop. The issue, barely noted in the weeks prior to the 2016 referendum, continues to dominate attempts to strike a withdrawal deal ahead of the March 29 deadline.

Writing in the newspaper, May said: “When I return to Brussels I will be battling for Britain and Northern Ireland, I will be armed with a fresh mandate, new ideas and a renewed determination to agree a pragmatic solution that delivers the Brexit the British people voted for, while ensuring there is no hard border between Northern Ireland and the Republic of Ireland.”

But Baker suggested May was seeking just a “codicil” with the EU, rather than a reopening of the Withdrawal Agreement negotiations.

He tweeted: “Leave-backing MPs voted to support alternative arrangements in NI but with grave misgivings about the whole agreement.

“Now the PM co-opts us into accepting everything but the backstop and, on the backstop, accepting a codicil.”

Meanwhile, International Trade Secretary Liam Fox hinted he could support a delay to Brexit, despite previously speaking out against an extension to the Article 50 period.

He told Sky News’s Ridge on Sunday show: “That was in the context of us not having reached an agreement [with the EU] and simply extending the time. I don’t think that solves anything.

“If we actually have an agreement and it takes a little more time to get the legislation through to make that as smooth as possible, I think that’s a very different argument.”

When pressed further, he added: “If we have an agreement and we need some time to get the legalities done, that is one thing.

“To extend simply because we hadn’t reached an agreement would not provide any impetus for that agreement to be reached and in any case, there is no guarantee the EU would want to do that.”

On the chances of a no-deal withdrawal, he said there was a need to guard against “an irrational pessimism that says that everything will be a catastrophe and irrational optimism which says everything will be OK,” adding: “The truth lies between the two.”

Appearing on The Andrew Marr Show, Home Secretary Sajid Javid dismissed reports that a snap General Election could be held in June if May cannot win parliamentary approval for her Brexit deal before the March 29 deadline, saying this is “the last thing this country wants”.

When repeatedly asked if a no-deal Brexit would make the UK less safe, Javid conceded there could not be a “like-for-like capability” on security without access to shared systems.

These include the European arrest warrant system used to bring suspects to the UK. It was used to bring Marek Harcar to justice for the brutal murder of sales executive Moira Jones in 2008. He fled to his native Slovakia after the crime.

Javid said: “It is absolutely true that if we have a no-deal situation there will be certain capabilities that we rely on for security with the EU such as databases, arrest warrants, others, that of course will change.

“We have been working on mitigants and I’m not pretending for a second through Interpol or through the Council of Europe on extradition you can have a like-for-like capability. So there will be a change in capability.”

Urging caution, he went on: “There will be a change in capability but it’s worth putting it all in perspective.

“Most of these capabilities were only relevant for us from 2015 onwards and I’m absolutely certain as Home Secretary, this is my most important job, is to do everything I can to keep this country safe.

“I am absolutely confident that we will continue to be one of the safest countries in the world, even in a no-deal scenario.”

On the backstop, Javid suggested Border Force figures believe there are viable alternative arrangements that would avoid the need for a hard border between Ireland and Northern Ireland.

He told Marr: “I asked Border Force months ago to advise me, to look at what alternative arrangements were possible.

“They have shown me quite clearly you can have no hard border on the island of Ireland and you can use existing technology.

“It is perfectly possible – the only thing missing is a bit of goodwill on the EU side.”