Inflation is expected to hit a three-year high, landing the Government with a bumper bill for increased state benefits and underlining the squeeze on household incomes.
September's consumer prices index (CPI) will be used to determine next April's rise in the basic state pension, piling pressure on the public purse but bringing some relief for hard-pressed pensioners.
Based on City forecasts for CPI of 4.9%, the basic single state pension will increase by £5 to £107.15 a week, while the joint state pension will increase by £8 to £171.35. Employment benefits, such as Jobseeker's Allowance (JSA) and income support are also calculated using the September CPI rate, meaning the JSA could increase by £3.31 to £70.81 a week.
Elsewhere, Sir Mervyn King, governor of the Bank of England, which is tasked with keeping inflation down, is expected to mount a strong defence of the Bank's handling of the economic crisis in a keynote speech.
Next year's benefit rates are not formally unveiled until later this year and will be the first to be calculated using CPI rather than the retail prices index (RPI) rate of inflation, which is expected to rise from 5.2% to 5.4% in September.
Dave Prentis, general secretary of Unison, said: "The move from RPI to CPI to calculate pensions inflation will take millions out of pensioners' pockets - just as we need people to be spending to kick-start our flagging economic recovery."
The increase in state benefits will put more pressure on Chancellor George Osborne, who is battling to slash the nation's budget deficit, as unemployment hit a 17-year high of 2.57 million in the three months to August.
Some economists believe that inflation could spike at 5.1% - up from 4.5% in August - after price hikes from major energy providers, including Scottish & Southern Energy, E.ON, British Gas and Scottish Power.
The figures are unlikely to overly concern the Bank of England, which has already forecast inflation to rise to 5% this year and recently increased its quantitative easing programme in a sign that growth problems outweighed the threat inflation poses to the economy.
The inflation rate will underline the increasingly difficult conditions faced by households - after figures last week revealed weekly earnings grew at just 1.8%.