The head of the bakery chain Greggs has threatened the government with "a march of the bakers" as it steps up its campaign to block VAT on pasties with a national petition.

Amid ongoing embarrassment for the coalition over the surprise budget announcement of changes to VAT on hot takeway food – dubbed the "pasty tax" – Greggs' chief executive, Ken McMeikan, said the chain was inviting its 6 million customers to sign petitions at its 1,600 UK shops from Friday.

A petition has already been set up on Downing Street's online scheme by bakers' trade associations but in a Radio 4 interview McMeikan said Greggs would be launching its own.

McMeikan said he was concerned that the VAT imposition could force small, independent bakeries out of business, and pledged to join forces to block the proposal during the six-week consultation period.

"My concern is that many small bakers – independent bakers – have (already) gone to the wall. The bakery industry has always been a key part of the high street."

He warned that the chancellor could expect to face "a march of the bakers" as affected businesses joined forces.

McMeikan said that if the VAT rise went ahead in October, Greggs would have no choice but to pass it on to customers: "Something of this magnitude, regrettably, we would have to pass on to the customer. This price increase would be devastating."

The e-petition, organised by British Baker magazine in conjunction with the National Association of Master Bakers (NAMB), campaigns against what it describes as "a draconian move". The petition says: We intend to strongly emphasise the lack of thought in this ruling and that this could very well see the demise of many more small bakers' shops in the high street due to loss of custom. Customers visit their local bakers for pies and savoury product, as opposed to more expensive meats for their main meals, especially during the current economic climate."

The NAMB, which represents more than 1,000 craft bakers, said it was taking legal advice after claims that the controversial tax ruling may break EU laws.

The association's chief executive, Gill Brooks-Lonican, said: "We think we may have a very good case and will be talking to our lawyers. The response to the government's plans has been huge and critical. A lot of small independent bakers are already struggling and this could well push many of them over the edge."

She said the extra tax "was clearly not thought through properly and it will affect people who are already finding it difficult to feed their families".