The government has been warned it is badly underprepared for new border controls if Britain leaves the EU without a free trade deal.

MPs on the Public Accounts Committee (PAC) said the government's assumption there would be a comprehensive free trade agreement was "borderline reckless" and reflected “an over-reliance on wishful thinking.”

They say that the implications for the Port of Dover could be serious if plans for new infrastructure are not in place by March 2019.

The warning comes as it was announced that a deal had been reached with European Commission to progress talks on the UK's departure from the EU.

The MPs' report suggests the government needs to do more in the event of there being a hard Brexit agreement in 2019 - without any transitional period.

The report says “government departments need to step up and be prepared for the possibility of a no-deal scenario and for the costs of all potential options.”

It says the government’s Border Planning Group does not expect to have any additional border infrastructure in place by March 2019.

“This includes any infrastructure needed to undertake additional physical checks of goods in ports such as Dover, due to capacity constraints.”

Committee chairman Meg Hillier MP said: "Government preparations for Brexit assume that leaving the EU will present no additional border risks from freight or passengers.

"It has acted—or rather, not acted—on this basis.”

“This approach, in the context of what continues to be huge uncertainty about the UK’s future relationship with the EU, might generously be described as cautious.”

“But against the hard deadline of Brexit it is borderline reckless—an over-reliance on wishful thinking that risks immediately exposing the UK to an array of damaging scenarios.”

These include the threat that the UK’s border could be exposed to risks on day one of departure.

Ms Hillier said: "After Brexit, the number of decisions required about people or goods crossing could more than treble and more than quadruple respectively. These figures should concern all in government and in our view, its current approach is not fit for purpose."

The committee’s new report suggests officials are basing their work on the assumption that there will be a post-Brexit transition period after March 2019.

That would give them time to put in place any new border infrastructure which may be needed.