The British government has given up trying to cut record levels of immigration into the country, a former senior aide has claimed.

Nick Timothy, who was chief of staff to Home Secretary Theresa May until this year’s election, said there had been major infighting between his department and the Treasury on the subject.

He wrote on the ConservativeHome website that the Treasury wanted high immigration to boost its own chances of balancing the books: “There is a new reason why the Treasury is keener than ever on mass immigration. A bigger population means a bigger economy overall which means the effect of spending cuts increases when the deficit is measured as a percentage of GDP.”

In last week’s spending review, Chancellor George Osborne based his figures on predictions that net migration would be at least 180,000 per year, contradicting the government’s promise to reduce it to the “tens of thousands”.

He hopes that by increasing the total amount of tax collected through new arrivals, the economy will look healthier.

Mr Timothy added: “It is well known that the Home Office would like to reform the student visa system further, reduce the number of work permits issued to foreign workers, change the way the asylum system works, and win greater control of immigration from other EU countries.

“But many of these changes have been blocked already or will be blocked by other government departments, while the government’s stated policy of trying to control EU migration through benefits changes has been blown out of the water by its promise to introduce the biggest ‘pull factor’ of all: a new ‘living wage’ of £9 an hour by 2020.”

The revelations come despite a major election strategist warning the government this summer that it faces defeat at the next election unless it cuts immigration.

Lynton Crosby, who ran the Conservative Party’s election campaign and helped deliver its shock win earlier this year, revealed the results of a confidential poll that said nearly 40 per cent of people who voted for the party did so because they were worried about immigration.

The issue was ranked more important than any other, including health spending and European Union membership.