The huge project is one of three big pipeline project decisions to be pushed back to allow extra time for new ministers to properly consider plans.

The others include the £1.2bn Luton airport expansion and Associated British Ports planned £100m Immingham Eastern Ro-Ro Terminal.

A decision deadline on all three has now been set for 4 October.

Proposals for the new 14-mile road – of which 2.6 miles would a tunnel under the Thames linking Essex and Kent – were accepted by the Planning Inspectorate in November 2022.

The Government has already delayed its planned 2024 start by two years to cope with inflationary pressures.

Transport minister Mark Harper said the extra six months was necessary to allow appropriate time for any new secretary of state to consider the applications.

He added: “The Department will however endeavour to issue decisions ahead of the deadlines above wherever possible.”