The Green Party has rejected a £7,000 donation from one of country’s richest men because he is not a full UK taxpayer.

Antony Tabatznik, who is said to be worth £500 million, had his donation returned because his tax situation did not meet the party’s “strict ethical criteria”.

The donation was permitted under electoral law because Mr Tabatznik is registered to vote in the UK and has a house here.

However, his non-dom tax status means while he pays tax on his UK income, money accrued abroad is out of reach of the taxman.

Caroline Lucas, who is the party’s only Member of Parliament, said the money was returned as soon as his tax situation became clear.

The MP for Brighton Pavilion, said: “I’ve always championed tax and financial transparency and I look forward to a time when the rules on political party funding promote such transparency.”

South African Mr Tabatznik, 66, previously supported the Labour party and gave £5,000 to Tony Blair’s New Labour back in 1998.

However, the pharmaceutical magnate’s son, who worked with the party on sustainability issues, is believed to have persuaded his father to donate the cash to Dr Lucas.

It is understood the donation was made in March and sent back earlier this month.

Mr Tabatznik was named as the 199th richest person in The Sunday Times Rich List at the weekend with an estimated wealth of £500 million.

He recently sold his Stevenage-based Arrow Generics business for $1.75 billion.

The support of a high-profile millionaire and former Labour donor would have been a huge boost for the relatively cash-strapped party ahead of this month’s European elections.

But Dr Lucas explained the decision to reject the money was an easy one.

She said: “The Green Party received a donation from Antony Tabatznik but decided to immediately return the money as soon as it became clear that he has non-domiciled status, and is not a full UK tax-payer.

“The donation was lawful because Mr Tabatznik is registered to vote in the UK, but it did not meet the Green Party’s strict ethical criteria.”