Rural bus services will be lost if government funding is cut in next month's spending round, campaigners have warned.

One in seven bus journeys would be lost by cutting the main support for buses, said the Campaign for Better Transport.

This would cost the economy £3.7bn by 2022, according to figures obtained by the campaign using a Freedom of Information request to the Department for Transport.

Abolition of the bus service operators grant was threatened in the 2010 Spending Review but saved due to pressure from a range of organisations and MPs.

Now over 30 organisations – including the Rural Services Network – have written to the Chancellor demanding he maintain support for bus services in this year's Spending Round.

Modelling by the Local Government Association suggests that further pressure on local authority funding could see councils cutting all their support for bus services.

Estimates of even a 25% cut in local council support for buses show this would reduce passenger journeys by 14%, said the Campaign for Better Transport.

It would spell the end of local authority support for evening services, services in smaller towns and the end of Sunday buses as authorities struggle to make ends meet.

Buses had already taken significant cuts in Government support.

The 2011/12 Spending Review cut funding for local authorities' transport budgets by 28%, with a cut of 20% to the direct support all buses receive through the BSOG from April 2012.

One in five bus services supported by local council were cut or cut back in 2011/12, with over 40% of local authorities cutting bus services again in 2012/13.

With support for bus services having already faced significant cuts, the campaign fears that a further round of spending reductions could push many services over the edge.

This could lead to the collapse of entire networks, it warned.

Campaign for Better Transport chief executive Stephen Joseph said: "If government swings the axe at bus funding again it could spell the end for whole networks of services.

"There will be grave impacts on employment, education and communities."

The Campaign for Better Transport was calling on the government to protect bus funding and avoid cuts which would "tip many vital services over the edge".

The letter sent to Chancellor George Osborne calls on the government to safeguard spending on buses. It sets out how essential buses are to a diverse range of groups.

The main support provided to bus services is the Bus Service Operators Grant (BSOG), funded by the Department for Transport to the tune of £445m each year.

The BSOG works in a similar way to a fuel duty rebate and is the only Government support available to all bus service operators.

Over nine years, removing BSOG would save the Treasury £1.8bn.

But the Campaign for Better Transport said the Department for Transport's own figures showed that removing BSOG would cost the economy £3.7bn in lost time and revenue.