Failure to complete a new customs system by the date of Brexit in 2019 could cause food to rot at the UK border, a report has warned.
Westminster's Public Accounts Committee warned it would be "catastrophe" if the system was not ready in time and there was no viable fall-back option in place.
The report warns Government must do more to work with businesses and ensure contingency option in place well before January 2019.
In 2015, around 55 million customs declarations were made by 141,000 traders. The UK's exit from the EU could see the number of customs declarations which HMRC must process each year increase five-fold to 255 million.
The report warns that a failed customs system could therefore 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.
"This is a programme of national importance that could have a huge reputational impact for the UK if it is not delivered successfully," the report warns.
"The uncertainty regarding the outcome of UK-EU negotiations is a complicating factor but it should not be used by HMRC to avoid taking action now in areas including: scaling up the CDS service to handle 255 million declarations; ensuring a viable contingency option is in place well before January 2019; and communicating with traders."
'Tight timeline'
The report issues a stark warning that there could be financial as well as operational implications of not acting now. It says "delay is not an option".
"The Treasury needs to ensure there is funding in place to develop contingency options so that there are no barriers to continuity of service. HMRC also needs to do a lot more to work with the many businesses affected.
"Much remains to be done to have an effective Customs Declaration Service in place, on time, and that traders know how to use.
"We intend to keep a close eye on this programme and expect to review progress early in the Summer of 2018, following a further review by the NAO."
Public Accounts Chair, Meg Hillier MP 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.
Ms Hillier said HM Revenue and Customs (HMRC) was under "considerable pressure" to deliver the CDS on time, but does not have the funding to increase the capacity to deal with the "consequences of Brexit - nor to develop contingency options".
NFU's Director of EU Exit and International Trade Nick von Westenholz said there will be 'considerable disruption' if a deal is not secured with the EU.
