As attention is focused on the links between Mossack Fonseca, their wealthy clients and the billions they have invested in the London property market, it is easy to overlook that luxury homes in other major UK cities also form part of the investment portfolios of a moneyed offshore elite.

Dozens of expensive apartments in Birmingham's Orion Building, which is 28 stories-high with five basement floors and boasts the West Midlands city's first million pound-plus penthouse, are owned by firms based in tax havens.

Many of those apartments are connected to Mossack Fonseca, the offshore services firm at the centre of the Panama Papers expose, the largest leak in history which has seen 11.5 million secret documents fall into the hands of journalists.

Tax avoidance is legal, but politically controversial, particularly at a time of government austerity. Mossack Fonseca denies any wrongdoing and said it acts within the law at all times. It believes it was a victim of hackers, who obtained the files and leaked them to the media.

According to data from Land Registry, at least 64 of the 200 apartments in The Orion Building are owned by companies based in tax havens, including the Isle of Man and the British Virgin Islands, both crown dependencies where tax rates are significantly lower than the mainland.

"The tall blue glass tower of The Orion Building is an unmistakable sight in the Birmingham skyline and a true landmark in the centre of the city," says the building's website, which was completed in 2007. "[It] is widely regarded as one of the most prestigious buildings in the city centre with its wide offering of studio, one and two-bedroom designs.

"Sandwiched between The Mailbox and New Street, and right around the corner from Birmingham's latest hip urban pocket, John Bright Street, The Orion Building finds constant favour with those for whom location is everything."

Location really is everything for some of the apartments' owners, ideally offshore. More than a quarter of the apartments, 51, are owned by a company called Triward Holdings Limited, set up on the British Virgin Islands through Mossack Fonseca, which is listed as the proprietor for each one. It is not known who the beneficial owner of Triward is and IBTimes UK could not reach the company, which had no website nor traceable business address.

Other properties in The Orion Building are owned by BPG Investments Limited, Whispering Trees Limited, and Bajora Limited, all based on the Isle of Man.

"I'm truly appalled and I do hope that this doesn't have any impact on our residents," said Kath Hartley, a Labour party councillor in Birmingham, whose Ladywell ward is home to The Orion Building. "Offshore companies [are] awful, but it's not unusual for pension funds and so on, and even individual landlords and property management companies, to just buy up a block of apartments here, there and everywhere within a development — even before it has been built."

Investors in the British property market generally use offshore structures, such as companies or trusts, because it is cheaper in terms of tax when buying and selling homes. It is also more confidential because the owners can stay hidden behind offshore services companies, such as Mossack Fonseca, who will list themselves as the directors of offshore vehicles.

Both the British Virgin Islands and Panama are the two most popular tax havens used by Mossack Fonseca on behalf of its clients. The British Virgin Islands is also the largest single source of foreign ownership of UK property. There are 22,814 buildings in the UK with ownership stemming from this Caribbean tax haven alone, according to Land Registry figures, compiled by the Estates Gazette. Panama is eighth on the list with 2,039 buildings in the UK. The top 10 is dominated by tax havens, including Guernsey, Luxembourg and the Isle of Man.