Members of a gang who carried out a "highly sophisticated" £2.4 million VAT fraud have been jailed for a total of more than 24 years.

The gang of six were found guilty of conspiracy to cheat the public revenue following a trial at Southwark Crown Court, HM Revenue and Customs (HMRC) said.

They used insider knowledge provided by former HMRC worker Susanne Green, 38, from Elgin, Moray, to fraudulently claim millions in VAT repayments.

A three-year investigation found the former tax office employee had used her position working in the Electronic Payments Team in Southend, to identify unallocated VAT payments - a payment made by a trader or individual which has insufficient details to enable HMRC to correctly allocate it to that traders' account - and fraudulently pay them elsewhere.

She used company details provided by accountants Michael Perry, 46, from Essex, and Daniel Weidner, 47, from Hampshire, to fraudulently misallocate VAT payments to specified businesses.

The investigation found that Arthur Lee, 55, from Essex, who was in a relationship with Green, received details of unallocated payments from her and passed them to unqualified accountants Perry and Weidner, who then used their clients' companies to claim the VAT payments for themselves.

Joff Parsons, assistant director of Internal Governance Criminal Investigations, Fraud Investigation Services at HMRC, said: "Green, Lee, Perry and Weidner were at the forefront of a highly sophisticated fraud.

"As an HMRC employee Green was trusted with the sensitive information she was dealing with on a daily basis, but she abused her position and was pivotal to the theft.

"The defendants used a network of front companies to receive the fraudulent payments and to launder the proceeds.

"Had HMRC not stopped them, they could have attempted to steal millions more in a deliberate attack on the public purse but they are now facing over 24 years in jail as a result of their fraud.

"HMRC will not tolerate corruption at any level and will pursue those responsible and bring them before the courts."

Along with Lee two men - Londoner Michael Myatt, 56 and Stephen Maish, 54, from Wigan - allowed their identities and companies to be used as part of the fraud.

The investigation came to light when a legitimate taxpayer of an unallocated payment queried why their payment to HMRC had not credited its VAT account.

While investigating, a vigilant HMRC employee noticed that this payment had been misallocated and that a further three payments had also been misallocated to the same incorrect trader.

In all four instances the payments had been handled by Susanne Green.

The gang were sentenced on December 5, HMRC said.

Green was jailed for five years and six months and a further two years to run concurrently for a second charge while Lee was jailed for four years and six months and, for a second charge, a further two years and six months to run concurrently.

Weidner was jailed for five years and six months, Myatt and Maish for two years.

All five had pleaded not guilt to conspiracy to cheat the public revenue.

Perry initially pleaded not guilty but changed his plea to guilty during the trial and was jailed for five years and three months.

Lee has been disqualified from being a director for five years, Myatt and Maish for three years.

Confiscation proceedings to recover the gang's criminal profits are ongoing, HMRC said.