Britain's prime minister says a government-backed investigation into the west London apartment block fire that killed at least 80 people will focus on the causes of the blaze and regulations for high-rise buildings.

The terms of the Grenfell Tower inquiry will sidestep wider issues around social housing that many residents had wanted to include.

Prime Minister Theresa May says she's determined broader issues will not be "left unanswered." However, she says Martin Moore-Bick, the retired judge leading the probe, will focus on the crucial question of what caused the fire and "learn the lessons to stop a similar catastrophe happening in the future."

Britain has been testing cladding systems in place on tower blocks in the weeks since the June 14 blaze, which began in a refrigerator and quickly spread throughout the 24-story building.