Brexit may be delayed beyond the planned March 29 withdrawal date to ensure the UK is fully prepared for leaving the EU, cabinet minister Andrea Leadsom has suggested.

The Commons leader said she believes the government has enough time to pass the legislation necessary for the country to be ready to leave the EU.

But she became the first senior minister to publicly acknowledge the exit process may become more drawn out than planned on Friday.

Leadsom insisted the extra time may not have to be bought through an Article 50 extension – which would risk enraging her fellow Brexiteers – but instead through a short period of “goodwill” granted by the EU.

She told BBC Newsnight: “We can get the legislation through and I think we do, in spite of everything, have a very strong relationship with our EU friends and neighbours and I am absolutely certain that if we needed a couple of extra weeks or something then that would be feasible.”

Asked whether the situation she described would mean an extension of Article 50, Leadsom, who manages the timetabling of Commons legislation, said: “It doesn’t necessarily mean that.

“Think carefully about it. With goodwill can still get legislation through in good time.”

Theresa May has so far insisted Britain is leaving the EU as planned on March 29, but has refused to rule out an extension of the withdrawal process.

In remarks apparently aimed at Remain-minded cabinet colleagues like Amber Rudd and Philip Hammond who are opposed to a no-deal Brexit, Leadsom also urged ministers to get “on the same page” and ensure the country was ready for any eventuality.

The Tory minister also urged the EU to cave in and grant concessions on the Irish backstop that is driving much of the domestic opposition to the prime minister’s Brexit deal.

It came as Irish premier Leo Varadkar warned that soldiers may return to the border with Northern Ireland if there is a botched no-deal Brexit, while insisting he would not back down on the need for a backstop.

Varadkar told Bloomberg TV the border at present was “totally open” but that if things went “very wrong” it would “look like 20 years ago”.

Asked to describe what a hard border would look like if the outcome of Brexit was a worst-case, Varadkar said: “It would involve customs posts, it would involve people in uniform and it may involve the need, for example, for cameras, physical infrastructure, possibly a police presence or army presence to back it up.”

His comments have been criticised by Democratic Unionist Party MP Gregory Campbell, who said the taoiseach should “dial down the rhetoric”.

“This is deeply unhelpful talk. Varadkar knows full well the connotations of such statements and he knows it’s nonsense,” he added.

An Irish government spokesman issued a statement after the interview to clarify that Varadkar was not referring to the Irish army.

“The taoiseach made it clear in the interview that the government is determined to avoid a no-deal scenario and the consequent risk of a hard border,” the spokesman said.

“He was asked to describe a hard border, and gave a description of what it used to look like, and the risk of what it could look like in the worst-case scenario.

“He was not referring to Irish personnel and the Irish government has no plans to deploy infrastructure or personnel at the border.”