Plans to build an underground travelator to connect the London terminus of High Speed Two (HS2) with the Channel Tunnel Rail Link have been revived by the team behind the proposed £42.6bn HS2 railway.

Under present plans, HS2 would leave from Euston and would not be linked to HS1, better known as the Channel Tunnel Rail Link, which starts less than a mile away at King’s Cross St Pancras. The Government removed a direct, £700m HS1-HS2 single-track rail link last year, concerned that it would cause too much disruption.

But HS2 Ltd and Network Rail are looking at several options, including a travelator and splitting the line before it reaches Euston. This would mean trains could connect directly to HS1, but this time on a twin track that would allow trains to go up and down the link at the same time.

The result would be a seamless service from Manchester or Leeds, the two cities where the second, Y-shaped phase of HS2 will terminate when it is completed in the early 2030s. HS2 Ltd sources say this could be part of a “suite” of connections, which could also include a walkway between Euston and St Pancras.

However, a Network Rail director told The Independent on Sunday that a previously mooted travelator between the two stations was the likely “end game”. Rail experts fear that this could be an expensive option and would cause upheaval, because a tunnel would have to be built close to the surface between the two busy stations.

HS2 has been dogged by criticism of its hefty price-tag, which had to be increased by £10bn two years ago after design and construction costs had become clearer. HS2 Ltd has been more confident in its ability to build the railway within its revised budget since Sir David Higgins, who led the construction of the London 2012 Olympic Park, became chairman last year.

A leading rail consultant said he was concerned that transport officials had become “too emboldened” about HS2’s budget and were trying to “gold-plate” the railway. But other rail insiders said the Treasury was successfully applying pressure on HS2 Ltd to cut costs.

HS2 Ltd declined to comment.