Peers took part in a debate on the UK's global role, emerging powers and new markets, on 6 December 2012.
The subject for debate was tabled by Conservative peer and former Foreign Office minister Lord Howell of Guildford.
Earlier this year, Brazil's economy overtook Britain's for the first time, as the UK slipped from sixth to seventh in the ranking of world economies.
Brazil's total output in 2011 was worth £1.56 trillion - compared with £1.53 trillion in Britain, think-tank Cebr said.
The UK economy grew by just 0.8% last year and contracted by 0.2% in the final quarter, leaving the country on the verge of a double-dip recession.
In contrast, economic output rose by 2.7% in Brazil, which has a population of around 200 million people.
The United States still had the largest economy in 2011, with China closing the gap in second and Japan, Germany and France making up the top five.