Scottish fishermen evading tax have been warned they face heavy fines and potential prison sentences as part of a major crackdown.

Tax officials moved after the Scottish fishing industry was deemed "high risk" and aim to recover about £3.6 million from one of Scotland's biggest industries.

Her Majesty's Revenue and Customs inspectors want to root out those under-declaring catches, fixing their books or claiming benefits to which they are not entitled.

HMRC has set up a taskforce that will target crews, fishing vessel owners and fish processors, and anyone caught dodging tax will face a fine as well as potentially a criminal prosecution.

The new body, which was launched yesterday, will also work closely with Police Scotland, immigration officials, the Border Force and the Gangmasters Licensing Authority.

Although the taskforce estimates the figure it hopes to recover is £3.6m, HMRC sources admitted the scale of the problem is likely to be much larger.

An HMRC spokesman said the decision to target the Scottish fishing industry followed intelligence that there was a problem.

He added: "Our taskforces are sent in because we know there is a problem with compliance in that area. We do not send our guys off on fishing expeditions."

David Gauke, the Exchequer Secretary to the Treasury, said the vast majority of people working in the fishing industry were law-abiding and paid their taxes.

However, he added: "Their livelihoods are often undermined by those who do not play by the rules. We are determined to support those hard-working people who want to get on in this industry and every other. "

His views were supported by Bertie Armstrong, chief executive of the Scottish Fishermen's Association, who admitted the industry, like any other, contained tax-dodgers.

He said: "The HMRC has said the vast majority of those in the fishing industry pays the tax they are due.

"I am also recognising that these taskforces are set up across the country for a number of industries. It is not the industry that is being targeted, it is a small number of individuals."

He said all industries and professions had tax evaders, but added: "One reflection I would make is the figure they are looking to recover is quite small, over £3m, when compared with the turnover of the industry which is between £3500m to half-a-billion."

Jennie Granger, HMRC's director-general of enforcement and compliance, said: "Our message is clear – if you seek to evade tax or defraud the tax system, HMRC can and will track you down."

It is not the first time the Scottish fishing industry has come under the spotlight. A seven-year investigation, Operation Trawler, secured a number of convictions over "black fish" rackets.

It was triggered after the then Scottish Fisheries Protection Agency (SFPA) became suspicious about widespread illegal landing of fish.

Last year four skippers who admitted their part in such a racket at a Scottish fish processing plant were ordered to pay fines of more than £1m.

The men, all shareholders in the Fraserburgh-based Klondyke Fishing Company, breached European regulations to land tonnes of herring and mackerel between 2002 and 2005.

A court heard they set scales and computer equipment to give false readings of the fish.

Another fish processor, Alexander Buchan of Peterhead, created a secret pipeline which allowed fish to enter the plant without being weighed.

HMRC believes that part of the tax evasion problem within Scottish fishing could be a lack of education and poor bookkeeping.

A source suggested that those who were found to be in that predicament would be treated more leniently than those found to be deliberately not paying the correct tax.

A spokeman said that, if successful, the taskforce on fishing might be sent to investigate the industry in other parts of the UK.

HMRC also launched taskforces to crack down on tax evasion in the holiday industry in Blackpool, the Lake District and North Wales, while teams will also target road hauliers in Milton Keynes, Oxford and Northampton.