Image caption Researchers questioned 21 focus groups to find the income standard

A couple with two children now need to earn £36,800 a year to have a "socially acceptable" standard of living, an anti-poverty charity says.

The Joseph Rowntree Foundation said its annual minimum income study suggests families must earn a third more than in 2008, to live within social norms.

But the report has been dismissed as "mostly rubbish" by the head of think tank the Adam Smith Institute (ASI).

The government said it was committed to helping the UK's "most vulnerable".

The minimum income standard (MIS) study - commissioned by the charity from the social policy research unit at Loughborough University - suggests a rising number of UK people live below what the public believes is an acceptable standard of living.

This MIS standard includes earning enough to eat a balanced diet, run a car and heat the home.

Researchers questioned 21 focus groups made up of working families, pensioners and single people of working age on a range of incomes.

A couple with two children were said to need to earn a minimum of £18,400 a year each before tax; single people £16,400 a year, while the figure for lone parent with one child is £23,900 and a pensioner couple £12,000 each.

The study said families are being hit hard by a "dangerous cocktail" of rising costs and cuts in three main areas:

If, instead of thinking about the breadline, we consider what level of income is needed for an acceptable standard of living, the debate changes Do you live above the bread, butter and jam line?

Childcare: Minimum costs have risen by nearly a third since 2008

Travel: Bus fares have doubled since the late 1990s which when combined with cuts to public transport, means families with children now deem a car as an essential item

Benefit cuts: Earning requirements have increased substantially, cancelling out the benefit of higher income tax thresholds

JRF chief executive Julia Unwin said families faced a "monumental task" to earn enough to get by.

"Parents facing low wages and pressure on their working time have little prospect of finding the extra money they need to meet growing household expenses.

"Many working people face the risk of sliding into poverty. It illustrates how anti-poverty measures are needed to address not just people's incomes but also the costs that they face."

The research also states that the level of Universal Credit - the government's new benefits system being brought in January 2013 - will strongly influence the ability of households to reach MIS.

'Silly question'

Both the results and methodology of the study have been questioned by Dr Eamonn Butler, director of the think tank ASI, who said the report was "mostly rubbish".

What makes up the MIS? Minimum weekly spend on some "socially acceptable" life essentials includes: Household goods and services: Childcare: £147.85, beds and bedding: £3.29, garden equipment: £0.66 Food and drink: Meat £18.08, vegetables: £11.27, snacks: £3.65 Social and cultural: Parent social activities: £30.00, UK holiday: £18.52, birthday gifts: £8.42 Transport: Car: £60.25, public transport: £12.38, Cycling: £1.40 Based on a couple with two young children with a weekly income of £685 More on what defines MIS

"If you ask a silly question you get a silly answer and I think this is a very silly answer.

"The idea that one needs a laptop, a DVD player, a microwave, a blender and a roof rack on your car and so on, and indeed a car in the first place when most of us live in cities and public transport has not actually changed very much in the last five years are very strange answers."

Dr Butler added that the study risks arousing people's expectations around welfare payments when "most of the public (75%) think benefits are too high".

But the study was defended by its co-author Donald Hirsch, who said the research was "significant" and "hugely robust".

"In terms of reliability... we have held over 100 groups over a period. Each group is checking back on what other groups say.

"It is not just one person at the ASI's opinion, it is groups of people coming to agreement... and then confirming it with subsequent groups," he added.

The government said it was forced to make "tough choices to repair the country's finances".

A spokesperson added: "It is vital that we give young children the best start in life and that is why we are rolling out free early education, backed by more than £1bn, to help children and their parents.

"We recognise that child care costs are an issue and that is why the prime minister launched a commission into this matter which will report back in the autumn.

"We are also introducing Universal Credit from 2013, which will simplify the system and ensure that work pays."

* Excluding council tax ** If both members of couple work full time