The banner called for a property act for Wales

From the tallest tower, they unfurled a banner which read "Property Act - Housing for local people".

Protestor Dafydd Tudur said the castle was picked for the event because it is "part of our heritage".

He added: "Our Welsh-speaking communities represent a much more important national inheritance."

In a statement, the society said north Wales' "serious housing crisis" was undermining Welsh-speaking communities.

The protesters stayed on the tower around four hours and said it was timed to highlight the issue to hundreds of Easter Monday visitors to the castle.

Mr Tudor said: "Since we are now on the verge of an election campaign, it is vital that Cymdeithas yr Iaith (Welsh Language Society) pushes the housing crisis to the top of the political agenda, in order to make sure that the issue is discussed.

'National inheritance'

"We believe that securing a property act for Wales is a means of alleviating the effects of the housing crisis, since such a measure would enable local people to gain access to the housing market, that house prices reflect the local market, that housing developments are based on local need and that there is an adequate provision of rented property.

"Caernarfon Castle is part of our heritage and as a result a great deal of effort has been made over the years to maintain it.

"However, it could be argued that our Welsh-speaking communities represent a much more important national inheritance, and therefore the Government should take urgent action by calling for a property act for Wales."

Mr Tudur claimed that the Welsh Assembly Government has "failed to deal effectively with the situation during the last two years".

"We hope that the Welsh Assembly Government will give us support in the call on the government in Westminster for an act which gives priority for local people to have houses in their areas," he said.

The Welsh Assembly Government declined to comment.