Mondays would become "fun days" if the Official Monster Raving Loony Party ruled the country and banned the first day of the working week.
Alan Hope wants to avoid the stress of Mondays
The party said it had collected 2000 signatures on its petition for a ban.
Standing opposite Parliament on a rainy Monday morning, party leader Alan Hope said "we hate Mondays".
He said "mundane Mondays" should be banned to prevent "stress-related health disorders" suffered by people as young as five.
And making a three-day weekend would not effect Tuesday's status - "Tuesday is Tuesday", Mr Hope, known as Howling Laud, said after singing a tune about how awful Mondays are.
He said that animals also suffered from stress on Monday because they had to get used to their owners not being around after a weekend spent together.
A photo opportunity to launch the vote-grabbing policy involved a dozen people with placards declaring "Just Say No to Mondays", and a giant Garfield - a cartoon character well known as someone who dislikes Mondays.
A fellow party member, known as Chinners, dressed in flamboyant clothing and hat, said the Monster party was the only one which campaigned when an election was not on.
"Monday is the most depressing day of the week. It would be good news to ban it - except for the Carpenters [who sing] Rainy Days and Mondays.
"Actually, we could move elections from Thursdays to Mondays and then we wouldn't have to have them," he enthused.
When his colleague questioned how a change of government would happen without any elections, Chinners altered his plan to say once the party was in power they would ban the day and change the election timetable.
Asked how the main parties would react to a Monday ban, Mr Hope said: "Labour would react laboriously, and the Conservatives would react conservatively."
The Official Monster Raving Looney Party has a long track record of standing in by-elections, where its candidates tend to celebrate even in the face of heavy defeats.
The Mondays campaign comes as the party's Loony Policy Unit puts the finishing touches to its Comprehensive Headwear review.