The All Party Parliamentary Small Shops Group had planned to reveal its findings into its inquiry into the changing face of the high street next week.
However, it says that it has since been flooded with additional evidence from independent retailers, consumers and lobby groups that Tesco may have breached planning laws.
Further new evidence also suggests that Tesco has used voucher schemes in an attempt to pull customers into its stores.
Jim Dowd, the Labour MP for Lewisham West in London who is leading the inquiry, has written to Competition minister Gerry Sutcliffe to highlight the new concerns.
It has now predicted that it will not be ready to report its findings until late January.
The fresh evidence follows Tesco’s admission at the inquiry that it may have been “overzealous” in building a store in Stockport.
Lucy Neville-Rolfe, Tesco’s company secretary, told the inquiry last month: “The people who were fitting out the store decided that they needed more space, mainly for backroom operation, and so therefore built the store bigger than the original planning permission.”