TV chat show host Michael Parkinson wrote off a substantial investment in a company used in a plan for earning tax relief when he decided the plan was not 'kosher'.

The company, Your Health International, was one of four companies that came under investigation by HM Revenue & Customs in relation to its alleged use by investors to benefit from charitable reliefs.

Parkinson's agent said this week that the TV star had put his money into the company which was briefly listed on the Channel Islands Stock Exchange as part of a plan to benefit from tax relief.

But when the nature of the tax plan became clear, Parkinson immediately pulled out, wrote off his outlay and did not claim relief available to him.

The tax plans under examination by HMRC involve companies that are floated. When the share price soars, investors gift the shares to charity. Investors can obtain 40% relief on the value of the shares, which may have soared many times in value.

The tax plans are legal, but are regarded as abusive by HMRC, which believes that many of the companies are simply cash shells and not genuine commercial undertakings. Vantis, which advised Parkinson, has insisted Your Health has clear commercial prospects and is not a cash shell.

It is not known how much money Parkinson committed to the plan, nor how much his shares rose on flotation. A shareholder register for the company shows that 416,000 shares owned by Parkinson were transferred on March 30 2006.

Parkinson's agent Neil Grainger told Accountancy Age this week: 'He certainly put his money into Your Health to get tax relief. We were assured it was approved by the Revenue. The minute we realised it wasn't kosher we dropped [it].

'We took the hit. We were very sensitive, extremely upset with the advice we got.'

Grainger said the advice came entirely from Vantis, but said he could not recall exactly when Parkinson pulled out of the plan. 'Rumours came up that the underlying charities were not over the moon about [the gifts],' he said.

He would not say which charity Parkinson made his gift to.

A spokesman for Vantis confirmed this week that the investigations into the four companies listed in the Channel Islands were understood to be ongoing. 'We've not heard anything [from HMRC],' he said.

The firm declined to comment on Parkinson's investment this week. 'We cannot comment on any individual's tax affairs.'

Vantis has argued that the HMRC's actions in respect of the four companies have been heavy handed, and that the firm applied the tax rules strictly.

Chief executive Paul Jackson said earlier this year: 'The American way is what Brown wants to bring in. That may take two to three years, [but you can] send out a message [this way]. There appears to be a clear campaign to rough up the mitigation sector,' Jackson said.