The UK is planning a package of emergency measures to boost housebuilding in London that could be announced as soon as Thursday.

The proportion of affordable homes developers must provide when trying to fast-track planning will be reduced to about 20% for non-public land from 35% under the changes, people familiar with the matter said, asking not to be identified as the information is private. The measures will also aim to simplify the viability of developing homes through changes to the appraisal process and a loosening of housing design rules, as well as several other moves aimed at boosting development, the people said.