Chancellor George Osborne has come under fire after he urged Chinese firms to pitch for contracts to build the controversial HS2 high speed rail link
With the HS2 Bill not expected to complete its passage through Parliament until the end of the next year, critics denounced the Chancellor's decision to launch the bidding process as "premature".
Campaigners against the line said that his appeal to Chinese companies to bid for construction contracts worth £11.8 billion made a "nonsense" of his claims the project would create thousands of jobs.
However the head of HS2 Ltd - the company established by the Government to develop the line - insisted no contracts would be let until the legislation had received its Royal Assent.
Chief executive Simon Kirby said they were seeking to draw on the technical expertise of firms in China - which has the world's largest high speed rail network - and that the project would create some 25,000 British jobs.
Mr Osborne launched the bidding for seven contracts, worth £11.8 billion, to build bridges, tunnels and earthworks on the first phase of the line between London, Birmingham and the North on the latest leg of his trade mission to China.
Speaking in the city of Chengdu, Mr Osborne also opened a pitch book on more than £24 billion of investment opportunities in the region he has dubbed the "Northern Powerhouse".
"We are truly entering a golden era of co-operation between our two countries, and it's crucial that businesses and communities from across the UK feel the full benefit of forging closer economic links with China," he said.
Richard Houghton of the HS2 Action Alliance said the move showed that it had become a "political project" to support Mr Osborne's ambitions to succeed David Cameron when he stands down as Prime Minister.
"This was meant to be a project that was going to not only build northern economies but also create jobs for British people. If the contracts are going to the Chinese it makes a nonsense of that claim," he said.
Joe Rukin of the Stop HS2 campaign group said that the expansion of China's high speed network had been dogged by cost overruns, a lack of sustainable growth and an inability to achieve the predicted passenger numbers.
"Sadly our Chancellor wants to jump into bed with the Chinese on this highly suspect project," he said.
Tory MP Cheryl Gillan, whose Chesham and Amersham constituency is on the planned HS2 route, said the launch of the bidding process was "premature" and questioned the long term future of the project.
"I wonder whether this still is a priority for Government considering that they have cancelled other very important projects in the North such as the Midlands electrification," she told the BBC Radio 4 Today programme.
However Mr Kirby said that it was important to use the period while the bill was going through Parliament in order to ensure the project delivered value for money for tax payers.
"We won't let the final construction contracts until we have parliamentary assent," he told the Today programme.
"High speed rail is new in the UK. China has the biggest high speed network in the world. It is about bringing the best technology into the UK."
Officials insisted that British firms would not lose out as a result of the decision to open up the bidding process to international contractors.
"We've made it a priority to engage with British firms to ensure they are well-placed to compete for the opportunities offered by HS2," a Government spokesman said.