The Institute if Fiscal Studies recently published some figures about a single-tier pension.
[http://www.ifs.org.uk/publications/6796]

I then under took some of my own research, and the cost to the state for just paying state pension, the numbers are vast.

11.58 million pensioners living in the UK. The basic state pension is £110.15 a week

Thus each year the UK pays £110.15 x 11,580,000 x 52 = £66,327,924,000 a year = £66,327 million

That is £66 Billion. (if everyone gets a basic pension of the £110.15 a week, some obviously get more, due to their higher national insurance contributions or in the State Enhanced Related Pension, known as SERPS), my number of £66 Billion is a much lower calculation.

The Institute if Fiscal Studies stated that today HM government actually pays £94,000,000,000 a year = £94,000 million = £94 Billion today in state pensions, the 2nd largest government expenditure after funding the NHS. The issue also is that is paid for by taxation and national insurance. There is no fundamental investment asset yielding an investment return, to pay for the state pension.

People deserve good pensions, the cost to the state is huge. But how huge ?
Government expenditure is about £700 billion.

Thus 13% (at least) of government spending is on state pensions today, and this is only going to rise as life expectancy rises, and also one has to accept that the basic state pension is simply not a living wage. Pensioners deserve good pensions. HM Government have no underlying asset to pay for our pensioners. The tax payer has to meet this payment, and to be honest, £110.15 a week is simply not a living wage.