The government has been issued a stark warning that trade with 70 nations risks "falling off a cliff edge" if it does not act quickly to roll over existing EU trade deals.
A report by the International Trade Committee argues there is "an urgent need for clarity" over the number, type, scope, extent and importance of the EU's trade-related agreements.
It calls for the Department for International Trade to produce "a legally watertight and practically viable strategy" to achieve "transitional adoption" of trade agreements the UK is currently party to through its membership of the European Union. But it said there was "a disturbing lack of precision" about which legal mechanism could be used.
The committee adds that government's request for the status quo to apply during transition is a "tacit admission... that its initial policy of negotiating new agreements by March 2019 may not be achieved".
As a result, "substantive amendments to rolled-over trade agreements will almost certainly be required".
One of the report's recommendations is that the government prepare for more extensive scrutiny and involvement by devolved governments on areas where changes to trade deals will require legislation.
A cross-departmental approach is "urgently needed", it adds.
Committee chair Angus Brendan MacNeil MP 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.
"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.
"Our report makes a number of practical recommendations, including the publication of a detailed timetable for avoiding a cliff-edge, and the development of a risk register in relation to trade and trade-related agreements that need to be rolled over. This issue requires a cross-Government response, and a fully transparent, cross-departmental approach to constructing the UK's overall long-term trade policy strategy."