A £23m purpose-built regional fire control centre which has sat empty for a decade finally has a tenant.
The control centre was built in Waterbeach, Cambridgeshire, in 2009, but the project was dropped in 2010.
The new tenant Wyzework now also claims delays in finalising an agreement cost the firm millions of pounds in revenue.
The Ministry of Housing, Communities and Local Government, responsible for the centre, said costs in the past two years had amounted to more than £4m.
The 30,488 sq ft (2,832.5 sq m) headquarters near Cambridge was designed to answer all emergency fire calls from Bedfordshire, Cambridgeshire, north Essex, Hertfordshire, Norfolk and Suffolk.
It was built as part of the last Labour government's plans to reduce costs by replacing county centres with regional fire control hubs.
The building was abandoned in 2010 after the Conservative/Liberal Democrat coalition government decided the plan could not "be delivered to an acceptable timeframe".
David Keegan, chief executive of business technical services firm Wyzework, said the tenancy was agreed in January 2018 but delays meant they did not get the keys until December last year.
The firm said it was forced to "cancel contracts with clients" because delays cost them a "considerable amount" of money.
A ministry spokesman said: "Whilst we have been liable for these costs [rent and services] we have done everything we can to reduce them wherever possible.
"The tenancy agreement was negotiated and finalised as quickly as possible."
The ministry revealed figures for the past two years for rent, rates, maintenance and services.
In 2017-18 costs were £1,995,394.25 and in 2018-19 they were £2,121,401.96. The government had been responsible for the building and its costs since 2009.
Fire Brigades Union regional secretary Riccardo La Torre has called for a review into how the centre was allowed to stand empty for a decade, while Cambridge's Labour MP Daniel Zeichner has called for a public inquiry.