Scottish companies who used RSM Tenon's tax avoidance service face more uncertainty over their liabilities, after the accountant's Premier Strategies subsidy was put into administration with the principal company.

Premier's sales rose from £2 million to £37m in six years to 2008, but was closed last March in response to the Chancellor's plans for a general anti-avoidance rule.

The subsidiary is said by close observers to have sheltered up to £1 billion for dozens of sizeable Scottish firms, avoiding £400m of taxes, in the decade to 2012.

Employee benefit trusts, the strategy at the centre of the Rangers big tax case where appeal judgement is still awaited, were Premier's best-selling product.

Earlier this year corporate clients received letters from the shut-down 'Premier Strategies' saying that after the Rangers case HMRC was "continuing to challenge EBT cases". RSM Tenon said its staff were handling client inquiries, despite having no dedicated staff in the area.

Baker Tilly bought Tenon's trading businesses from administrator Deloitte, whilst jettisoning Premier, in Thursday's pre-pack deal. The outcome, which wiped out shareholders, adds new uncertainty.

Meanwhile the five RSM Tenon partners in its Glasgow office who resigned in Baker Tilly's four-week offer period face a potential 18 months on the sidelines, twice the period expected by observers last week. The team led by Charlie Burton are believed to be intending to start their own venture, but despite the administration of RSM Tenon may still be subject to a six-month garden leave followed by a 12-month restrictive covenant imposed by their former employer.