The business and financial adviser believes that legislation which came quietly into effect late last year is poised to have a big effect on tax avoidance measures.
This could force banks to hand over information in relation to perceived serious tax fraud, with the same rule applying to lawyers and accountants.
Gary Ashford, a director within Grant Thornton's national tax investigations group, said: "After a lengthy period of consultation it was agreed that from 1 December 2007, certain provisions of PACE 1984 would apply to criminal tax investigations carried out by HMRC officers.
"For HMRC this means new powers of search, seizure and arrest in relation to unpaid tax."
This is already underway according to Ashford, who has spotted HMRC adverts for the recruitment of criminal investigation officers in London, Nottingham, Leeds, Manchester and Birmingham.
One area the new regulations could be utilised with immediate effect is against those that came forward during HMRC's Offshore Disclosure Facility (ODF).
Earlier this year, following requests for information from high street banks, HMRC offered a limited window of opportunity for taxpayers to get their affairs in order and disclose information left off their tax returns.
Ashford continued: "With the 26 November deadline having now lapsed, HMRC will now be risk-reviewing the disclosures they received for investigation. They will also be looking through the information they received from the five big banks to identify those who did not come forward."
"It's also likely that HMRC will embark on a second ODF. They are targeting another group of around 150 financial institutions in a bid to gain further customer details. Given these new rules it seems likely that HMRC will be successful in obtaining customer information relatively quickly."
Ashford is advising those who have undisclosed taxes to seek financial advice or risk the possibility of hefty tax bills.
