The Filpot normally carries adverts and is used in pubs and bars for discarded crisp packets and chewing gum.

However, the manufacturers have joined the campaign to help find Malton-born Miss Lawrence and have made 350 Filpots showing images of the chef and appeals for information on her whereabouts.

They are being distributed in pubs and other outlets across Yorkshire to assist in keeping Miss Lawrence's image in the public eye.

Miss Lawrence's father, Peter, made a fresh appeal for information on his daughter's disappearance.

Speaking from his home at Slingsby, he said yesterday: "I can't believe that it is now four weeks since Claudia disappeared.

"She was constantly around and we were regularly seeing each other in York, very frequently, and then all of a sudden it's just nothing.

"We know she's not been found in any of the search areas in York, but she's out there somewhere and we have had the main part of the Easter holidays, the Easter weekend and still, as far as I am aware, absolutely no leads at all as to where Claudia is."

Mr Lawrence said he was trying to remain positive but "felt absolutely dreadful" as the search for his missing daughter passed the four-week mark.

He admitted: "She could be absolutely anywhere."

He said he was grateful for the support he had received from family and friends and particularly over the weekend by the Archbishop of York.

"I spoke to him on Thursday for some length of time and he reiterated the fact that prayers are being said at Bishopthorpe Palace and that his house and telephone line are always open at the moment."

He added: "All I can say is to people is that she is out there somewhere. Someone must know where she is and hopefully either they or someone else who has seen her will have the courage to report it either to the police or one of the other organisations."

Shaun McDonnell, sales director of York firm Flourish Innovations Ltd – the manufacturers of the Filpot – said his company was not making any money out of the Miss Lawrence campaign.

He said he hoped the Filpot would be picked up by a brewery or hotel chain which could distribute the boxes nationally.

"I personally had a close relative go missing back in December 2006 and we spoke about it and obviously we know what Peter is going through and the rest of the family and we just thought if we could help we would. And that's basically why we did it," he said.

Miss Lawrence, 35, worked as a chef at York University.