The UK’s trade with more than 70 countries will “fall off a cliff” after Brexit, causing “significant” economic problems, unless the Government takes urgent action, MPs have warned.

The International Trade Committee said ministers need to “urgently” clarify how they will “roll over” trade deals with other countries that the UK currently has access to via the EU.

The Government’s failure to provide key details of this process will work is “disturbing” and risks causing a major hit to the economy when Britain leaves the EU, it said.

Ministers have said they intend to transfer the deals the EU has with more than 70 countries into new, bilateral deals between the UK and those countries after Brexit.

This would ensure Britain retains access to these countries’ markets even though it will no longer be a member of the EU.

However, the International Trade Committee said the Government must provide “a legally watertight and practically viable strategy”, warning there is “an urgent need for clarity” on the matter.

The Independent has previously revealed MPs’ concern that trade deals being rolled over will require significant amendment because the countries involved are likely to offer less favourable terms to the UK than the agreements they have with EU.

Conservative MP Jonathan Djanogly has tabled amendments to the Trade Bill that seek to ensure any changes must be approved by Parliament. Under current government proposals, ministers would be able to amend and agree deals without parliamentary scrutiny.

The International Trade Committee agreed that “substantive amendments” to the existing deals are likely to be required and said there was a “disturbing lack of precision and clarity” about how the Government plans to replicate them. Ministers should take steps to increase parliamentary scrutiny of trade agreements, it added.

SNP MP Angus Brendan MacNeil, the chair of the committee, said: “The Government is making much of the trade agreements it plans to make after Brexit, but first it needs to give us confidence that the existing agreements, on which businesses, consumers and trading partners alike rely, can be rolled over so the UK can benefit in its own right. Unless an agreement is reached with our trading partners in the coming months, a significant economic price will have to be paid.

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“The Government is therefore correct to have identified maintaining our rights under these agreements as a priority. However, as the Committee has found over the course of our inquiry, a number of thorny issues and significant risks remain unaddressed. The Government must not be naïve enough to assume that a verbal agreement to maintain the status quo constitutes a watertight guarantee – contingency plans are required.”

He called on ministers to publish a “detailed timetable for avoiding a cliff-edge” and adopt a “fully transparent, cross-departmental approach” to building a long-term trade policy.

The Government had previously said it would have the new deals in place by March 2019, but has since asked that the UK continue to be considered part of the EU’s existing deals during the post-Brexit transition period – suggesting, the International Trade Committee said, that ministers’ initial approach was overly ambitious.

The committee praised the Government for having made contact with the 70 countries quickly but warned that ministers “still need to work out a number of important details...as a matter of urgency”, including that exact number of trade deals that will need to be rolled over.

Greg Hands, the trade minister, said: “The report recognises the priority that the Government has given to ensuring continuity of our trade arrangements as we leave the EU, including in providing certainty to businesses, consumers and investors. We have always been clear that this work would take into account the terms and timing of any implementation period currently being negotiated with the EU.