The prince visited farms during the foot-and-mouth crisis

"The prince's involvement was entirely constructive and very much to the point", said Nick Brown.

Prince Charles is said to have intervened to try to prevent the slaughter of millions of cattle.

Mr Brown was speaking after NFU chairman Sir Ben Gill told the Times: "Charles was behind the biggest push for vaccination."

I'm sure the Prince of Wales seeks to express his views and makes them felt on a variety of subjects Sir Ben Gill NFU chairman

The North East MP told BBC Radio 4's World at One: "I was the agriculture minister for three years and I enjoyed the interest the prince took in these matters and his involvement was entirely constructive and very well informed.

"He had some very interesting things to say. So from my point of view I welcomed it."

The case for vaccination was "perfectly reasonable" and one the government considered, Mr Brown said.

But he said the government continued with the slaughter as vaccinated product would not be marketable.

Strict protocol

The article in the Times claimed the prince had launched "a personally orchestrated campaign" to put pressure on Tony Blair to stop the slaughter.

Speaking before the first day of the NFU's annual conference in Birmingham on Monday, Sir Ben had played down his newspaper comments.

Sir Ben will step down as NFU chairman after the conference

"I'm sure the Prince of Wales seeks to express his views and makes them felt on a variety of subjects and I have no reason to believe he did not at this time," he told the BBC.

"It is not news that the Soil Association and the organic movement as a whole championed the cause of vaccination as a way of bringing the outbreak to a close and of course Prince Charles is closely involved with the organic movement."

There is strict protocol that members of the Royal Family should not get involved in party politics.

During the outbreak the prince made a �500,000 donation to farmers and cancelled a skiing trip to show his support for their plight.

A spokeswoman for Prince Charles said: "The prince is regularly in touch with senior policy makers on a wide range of issues but such discussions are private."

She added: "The Prince of Wales was very concerned about the countryside and spent a lot of time talking to farmers and trying to find out what could be done to help them."

The NFU conference is taking place at the Hilton Birmingham Metropole on Monday and Tuesday.