MPs say that a failure to introduce a new customs system by the time of Brexit would be catastrophic and lead to massive queues at Dover.

The influential all-party Public Accounts Committee has warned that if the new Customs Declaration Service planned to be brought in is delayed, it would result in food rotting in trucks at the border and serious congestion.

The UK's exit from the EU could see the number of customs declarations which HMRC - HM Revenue and Customs - must process each year increase five-fold to 255 million.

A report issued by the committee today states: “A failed customs system could lead to huge disruption for businesses, with delays potentially causing massive queues at Dover and resulting in food being left to rot in trucks at the border.”

The MPs say the uncertainty surrounding the outcome of UK-EU negotiations is a complicating factor but it should not be used by HMRC to avoid taking action now.

These include “scaling up” the CDS service to handle 255 million declarations and ensuring a viable contingency option is in place well before January 2019.

MP Meg Hillier, the chairman of the committee, said: “Failure to have a viable customs system in place before the UK's planned exit from the EU would wreak havoc for UK business, trade and our international reputation. Confidence would collapse amid the potentially catastrophic effects.'

It was “deeply troubling” that HMRC did not have the funding to develop customs systems for Brexit or plan contingencies.

“This is a programme of national importance that could have a huge reputational impact for the UK if it is not delivered successfully.”

She said HMRC needed a relatively small sum to upgrade the current system but had been told by HMRC it was merely 'in conversation' over upgrade costs. “It should be banging on the doors of the Treasury.”

A Government spokesperson said: “The Customs Declaration Service (CDS) is on track for delivery by January 2019 and has the capacity to deal with a significant increase in customs declarations at the border.

"We’ve already allocated over half a billion pounds in funding to ensure a successful exit from the EU and we will have a fully functioning UK customs service on day one post Brexit.”