HS2 bosses have insisted they “learnt lessons” after it emerged they had made £1.76 million of unauthorised payments to staff.

But they insisted the planned high speed rail network, which has already cost £4.1 billion, would provide a huge boost to the UK’s economy lasting 100 years.

Tom Kelly, director of stakeholder engagement at HS2, told BirminghamLive that HS2 had already bought jobs to the city by attracting employers such as HSBC.

He said: “Birmingham is the big winner from HS2. Birmingham becomes the centre of the transport system in this country.”

Construction of the HS2 line, running between London, Birmingham, Manchester and Leeds, begins next year.

An artist's impression of the concourse view looking towards Station Square at the planned HS2 Curzon Street station

But the project, expected to cost £55.7 billion in total, continues to come in for criticism. Boris Johnson, the former Foreign Secretary who is seen as a potential Tory leadership candidate, suggested in a newspaper column earlier this month that it was too expensive.

The Commons Public Accounts Committee last year accused HS2 Ltd, the government-owned business managing the project, of “a shocking waste of taxpayers’ money” after it made £1.76 million of unauthorised payments to staff through compulsory and voluntary redundancy schemes.

Mr Kelly said: “As we acknowledged, at times our processes have not been all that they should be.”

Highlighting a more complimentary report from the National Audit Office, he added: “But As the National Audit Office said last week, our processes are improving and have improved considerably. And we have learnt lessons.

“That’s the same with every single infrastructure project. You learn lessons as you go along.”

HS2 route map
HS2 route map

Birmingham will be at the centre of the new rail network with a high speed rail station at Curzon Street, in the city centre, while a second station will be built near Birmingham Airport.

Mr Kelly said knowledge that the rail line was coming had already attracted employers such as HSBC, which will employ 2,500 at its new UK headquarters in the city, and others such as PWC.

“The knowledge that HS2 is coming has prompted HSBC to move people there.

“PWC, KPMG, Deutsche Bank - so the knowledge that HS2 is coming is already leading to investment.

“That investment wouldn’t happen without HS2.”

The HS2 project currently employed 7,000 people, he said, and the number would increase to 15,000 in 18 months and 30,000 in five years.

“Then there will be steady numbers of people employed in this project right up to 2033.

“That means people can have certainty that they can have a career in HS2 that will last them two decades.

“That means this country is investing in an up-skilled workforce that will make us more competitive in the global economy.

“That will be a substantial contribution to creating employment both in itself but also by creating a legacy of an asset that will last for over a century.”