Andrew Tyrie, the chairman of the Treasury Select Committee, has asked George Osborne to respond to suggestions from Barclays that retrospective tax action taken against the bank earlier this year was "unwarranted".
Barclays has put its $6.1bn stake in US fund manager BlackRock up for sale in a surprise move.
There were fiery exchanges at Barclays' AGM today, as shareholders grilled CEO Bob Diamond over his pay packet, the PPI mis-selling scandal, and the value of the bank's shares.
Some Barclays shareholders are expected to vote against the pay of its top executives at the bank's annual general meeting on Friday.
Barclays has seen its payment protection insurance (PPI) exposure rise by £300m in an indication other banks may also face higher bills for the mis-selling of the insurance.
Adjusted profits at UK lender Barclays surged by over a fifth in the first quarter of 2012, well above expectations.
Barclays has bowed to pressure from shareholders ahead of its AGM by putting a new clause into boss Bob Diamond's bonus package which could cut his payout in half.