Construction of a £1.4bn Heathrow spur link for HS2 has been ruled out by transport secretary Patrick McLoughlin.

McLoughlin confirmed the decision in a written response to a question by Beaconsfield MP Dominic Grieve. It was originally understood that a final decision over this link would be held until after the Davies Airport Commission reported in the Spring.

However, McLoughlin’s statement on Monday said: "I would now like to make clear that we do not intend to build the spur as part of Phase 1 or 2 of the HS2 scheme.”

HS2’s originally planned connection to the airport via a rail link from Old Oak Common is now the preferred, and only, option on the table. This would require travellers from the north having to switch trains at the interchange to head back towards Heathrow using the existing rail network.

"I would now like to make clear that we do not intend to build the spur as part of Phase 1 or 2 of the HS2 scheme.” Patrick McLoughlin, transport secretary

The reasons behind McLoughlin’s decision to press ahead with this announcement now remain unclear.

However, McLoughlin’s decision appears to follow pressure on the project’s cost and reports this week that Labour now plans to review the £21.2bn cost of HS2 phase 2 if the party wins the general election in May in a bid to bring down the project bill.

The potential Heathrow spur link had been switched into phase two of the project from the £21.4bn phase one, subject to detailed review, and a final decision had been expected to wait until after the Davies Commission’s conclusions on the preferred siting of a third runway in the south east. McLoughlin said in his written answer: "In November 2014, the Airports Commission published a high-level review of the implications of a HS2 spur on surface access to Heathrow Airport, as part of the supporting technical documents for their public consultation on the three short-listed schemes for airport expansion. This review indicated that an HS2 spur is highly unlikely to be necessary to support any expansion of Heathrow airport."

Heathrow Airport said in a statement:  “Whilst the HS2 spur is not part of our case for expansion, we do believe cities in the Midlands and the North would benefit from the shorter journey times to the UK’s hub.”

Meanwhile two new reports were published by HS2 this week, by Atkins, to evaluate the costs and practicality of converting a viaduct through the Colne Valley into tunnel

The proposed northern extension of HS2 Northolt Tunnel is supported by the London Borough of Hillingdon and the Colne Valley Community and includes provision for linking to a possible spur tunnel to Heathrow.

The reports put the additional costs of tunnel over viaduct at between £185M and £365M.