Detective Sergeant Tom Napier, of Humberside Police, was due to appear on the BBC One show Crimewatch last night to find Mark Daly and Carol Canham.
The pair were staying at a friend's house in St Leonard's Road, Beverley, in February when they "betrayed her trust" by stealing from the house.
Speaking to the Mail ahead of last night's live broadcast, Det Sgt Tom Napier said: "This was an extremely serious crime that Humberside Police urgently require information on.
"The crime happened between February 1 and February 18 this year.
"A large amount of jewellery was taken when Mark Daly and Carol Canham were staying at a friend's house.
"Unfortunately, they either decided before their stay or during the stay that they would betray that friendship and steal a substantial amount of jewellery.
"This was obviously very distressing for the victim and she desperately wants her items back as soon as possible."
Mr Daly, 42, has links to Coventry and Leeds. He is 6ft, with short, dark receding hair, blue eyes and a Midlands accent.
He has a large tattoo on his upper back with the names Lucas and Johnny in a jigsaw pattern.
Ms Canham, 48, had links to Beverley as well as Alicante, in Spain. She is about 5ft 8in and speaks with a Yorkshire accent.
Det Sgt Napier said: "Police are keen to track these two people down as soon as possible.
"We have been unsuccessful to date and that is probably because the two have connections in the Midlands and abroad.
"We contacted Crimewatch because we felt the need to appeal to the whole country.
"We are hoping some of their associates may get in touch with us.
"The other possibility is that the suspects may have other victims out there who want to get in touch with us.
"We would urge anyone with any details at all to come forward and help in our investigation."
The appeal was due to be aired last night in a programme to mark Crimewatch's 30th anniversary. It was filmed in Cardiff.
Anyone with information about the pair should call Det Sgt Napier at Humberside Police on 101.
Alternatively, call Crime- stoppers anonymously on 0800 555111.
