Mittal, 61, and his family's worth came down by 4,814 million pounds, but they were still the richest in Britain with a net worth of 12.7 billion pounds, according to the Sunday Times Rich List, which annually releases the worth of Britain's wealthiest individuals.
Mittal is marginally ahead with the Russian iron ore magnate, Alisher Usmanov, who takes the second place with an estimated worth of 12.3 billion pounds.
Indian-origin industrialist brothers, Sri and Gopichand Hinduja were the fourth richest in the list with a net worth of 8.6 billion pounds, 'The Sunday Times' said in an advance release on Saturday.
The newspaper's research reveals that the rich got richer over the last year, despite a global recession the combined worth of the country's 1,000 wealthiest people was 414 billion pounds, which is an increase from last year of 4.7 per cent.
Rich List compiler Philip Beresford told Sky News: "Obviously it's very difficult in this age of austerity...and the rich seem to be getting richer and richer. However, I would caution against bashing the rich because a lot of the people on this rich list are based here, they're investing in companies here, and if they get richer hopefully the rest of us will get a bit more prosperous on the rising tide of wealth."
The number of billionaires in the list is 77, with individuals needing to have at least 72 million pounds to make the top 1,000 individuals.
After Mittal and Usmanov, third on the list is Chelsea owner and oil baron Roman Abramovich, with a net worth of 9.5 billion pounds. The richest woman is former Miss UK Kirsty Bertarelli, with 7.4 billion pounds, while the Duke of Westminster's property portfolio is worth 7.3 billion pounds.
Harry Potter creator JK Rowling's worth has risen by 30 million pounds in the last year to 560 million pounds, putting her 148th on the rich list.
The top ten richest individuals in Britain are (in pounds): 1 - Lakshmi Mittal and family - 12.7 billion. 2 - Alisher Usmanov - 12.3 billion. 3 - Roman Abramovich - 9.5 billion. 4 - Sri and Gopi Hinduja - 8.6 billion. 5 - Leonard Blavatnik - 7.58 billion. 6 - Ernesto and Kirsty Bertarelli - 74 billion. 7 - The Duke of Westminster - 7.35 billion 8 - David and Simon Reuben - 7.08 billion. 9 - John Fredriksen and family - 6.6 billion. 10 - Galen and George Weston and family - 5.9 billion.