Described as white, of short stature and with a distinctive patch on its lower back, the bird was seen choosing a packet of salt and vinegar crisps then legging it out of Greggs.
Video footage shows the bird strolling up to the counter than rushing away once it has the goods in its beak.
It seems like it has done this before, as it is well acquainted with how to use automatic doors.
Witnesses saw the crime at a bakery on Kings Street in the centre of South Shields, Newcastle on September 2.
Gordon Lindsay, who filmed the incriminating footage, said: ‘It clearly just saw its opportunity and just went for it.
‘It grabbed a packet of Walkers Salt and Vinegar – it seemed clear that he knew what flavour he wanted.
‘The staff at the time were filling up the coffee machine and they didn’t see him until he was leaving – so there wasn’t much they could really do.
‘They were quite surprised, and so was I. I just thought it was unbelievably cheeky.’
The seagull is thought to be still at large.