Jobs in the north of England are being lost at four times the rate in the rest of the country, deepening the economic divide and prompting new calls for devolution of powers to an elected assembly for the north. About 98,000 jobs were lost in the north-east, north-west, Yorkshire and Humberside in 2011, according to an analysis by the centre-left thinktank IPPR North. This was an 18% increase on the previous year, dwarfing the 4.5% rise in the rest of England. In the most extreme case, in the north-east, 12% of the working-age population are unemployed compared with 6.5% in the south-west, 6.4% in the south-east and 9.9% in London.

The figures will bolster the growing movement calling for a "voice for the north" through an elected assembly. In the Observer, a letter from six Labour MPs from across the north, supported by parliamentary colleagues from other regions, says that the debate over Scotland's potential move to further devolution or independence should not "ignore the growing political marginalisation of the north of England, with a cabinet dominated by southern politicians who seem to know little, and care even less, of the economic and social problems of the north".

It demands that the north is given a "stronger say in its own destiny" and calls for a debate on the benefits of directly elected regional government. The MPs, who are patrons of a new thinktank, the Hannah Mitchell Foundation, established to campaign for an elected assembly, said: "We need to move on from the pessimism that descended on politicians after the defeat of the referendum for north-east devolution in 2004, and recognise that the UK has changed."

Barry Sheerman, the MP for Huddersfield and a signatory of the letter, said the movement aspired to create an assembly, but in the short term he believed that each region should have a commission made up of business and academic leaders to protect its particular interests.

"I am very passionate about this. The north has a much larger population than Scotland, and look at London, which has an assembly and a powerful mayor to protect its interests. With the scrapping of the regional development agencies, we don't have a body to deal with strategic problems and issues for the north.

"As I keep telling the prime minister and chancellor, the northern regions have been in recession for years."

Linda Riordan, MP for Halifax, said: "The disparities between the north and south are widening and demand action and it is extraordinary that the government is getting rid of the regional development agencies that provided us with some support."

The government is funding 164 projects through a regional growth fund, "creating and safeguarding" more than 330,000 jobs, supported by more than £6bn of private investment. In November, the chancellor announced an additional £1bn for the fund, bringing the total to £2.4bn.