Alun Michael, the rural affairs minister, has been forced to cancel another appearance on police advice.

Michael had to scrap a boat trip after pro-hunting protesters arrived in a small flotilla off the Dorset coast and threatened to pursue him.

He is scheduled to speak at the annual conference of the Association of National Parks Authorities tomorrow, but a spokeswoman at the Department for the Environment, Food and Rural Affairs said: "It is recess. The diary is fluid and we do not routinely announce ministers' engagements each day."