Hundreds of bakers are set to march on Downing Street during a day of action over the controversial "pasty tax".
About 300 pasty manufacturers will gather on Whitehall to object to George Osborne's bid to make hot takeaway snacks subject to 20% VAT.
The march, organised by high street bakery chain Greggs and the National Association of Master Bakers, will start at Pudding Lane.
Six representatives from the baking industry, joined by Cornish MPs, will later present a petition of nearly 500,000 signatures to 10 Downing Street.
Stephen Gilbert, MP for St Austell & Newquay, hopes politicians will be lured by the taste of an authentic Cornish pasty when he hosts a campaign event in the Houses of Parliament. The Lib Dem MP will team up with the Western Morning News to hand out baked goods from the Proper Cornish Pasty Company in an attempt to garner support.
Mr Gilbert said: "Opposition to George Osborne's proposed "pasty tax" is continuing to grow. I urge the Government to listen to the strength of feeling being demonstrated today and review their unworkable and damaging proposal.
"It is simply wrong for the Government to impose a tax on the humble Cornish pasty while luxurious caviar remains tax-free. If these plans go ahead, it could result in 400 job cuts and losses to the Cornish economy of £7.5million. My fight in Parliament will not stop until these plans are dropped and I urge everyone to continue to sign the petition."
Representatives from bakeries across the country who attend the protest outside Downing Street are also being encouraged to meet with their local MP and explain the impact that the VAT move would have on the local economy in their constituencies.
Last week a move by Labour to block the "pasty tax" was defeated despite a revolt by 14 coalition backbenchers - nine Tories and five Liberal Democrats.
The Prime Minister previously told the Commons he understood why "feelings in Cornwall run high on this" but insisted it was unfair that other takeaway food was covered by the tax while pasties were not.