Questions are being asked about the reliability of intelligence compiled by the authorities on terrorist suspects.
However, changes to both UK and EU legislation to counter cross border fraud mean that fiscal law and intelligence is also increasingly being used as a weapon in the war against terror, with money laundering and tax evasion in particular being targeted by a range of legal and financial authorities.
It could all result in more tax investigations.
Gary Ashford, senior manager in the tax investigations team at Grant Thornton in Birmingham, said: "The European Union in particular has been spearheading a drive to increase co-operation between member states in the fight against fiscal fraud for quite a while. The wider international community via the OECD also sees this as an effective approach.
"The various fiscal authorities are seen as financial 'gatekeepers'. The terrorist attacks on 9/11 and 7/7 provided further impetus for action as the proceeds of criminal activity are often used to fund such attacks and the groups behind them.
"Making it easier to follow financial transactions across international boundaries is crucial if the intelligence agencies are to be able to track activity in this way."
A number of different types of frauds are currently being targeted by evolving legislation, including so-called 'carousel fraud' and off-shore bank accounts. Mr Ashford continued: "The recent Barclays bank ruling indicates that the Revenue suspects that about 20 per cent of overseas bank accounts contain untaxed income or capital.
"That same ruling is now forcing banks to reveal details of their clients' offshore accounts to HMRC and will not only have repercussions for account holders but will also provide a wider opportunity for the intelligence agencies too.
"Changes to the Govern-ment's anti-money laundering strategy are also being used to highlight suspicious activity to intelligence agencies.
"The Proceeds of Crime Act 2002 requires that any professional involved in financial activities must report suspicions or knowledge of a client's money laundering to the National Criminal Intelligence Service.
"In fact, they can now face criminal prosecution if they fail to do so.
"While safeguards are in place to protect the identity of the intelligence source in such cases, it is clear that there is a real shift towards greater s haring of information between all fiscal authorities that can only be of benefit in the fight against terror.
"It is important that on a local level, this approach will have a real indirect benefit to HMRC which will now be able to access far more information than has previously been the case.
"This in itself is likely to lead to an increase in the number of investigations."