Three months into his reign as London mayor, Boris Johnson is to face a formal investigation by the London Assembly into his mayoral appointments following several recent embarrassing resignations. The probe, which will be handled by the assembly's business management and administration committee, will examine if proper procedures were observed by the mayor and the advice he received by officials.

The inquiry, chaired by Green Party member Darren Johnson, will concentrate on the mayor's post-election appointments and will seek to identify how the Greater London Authority can learn from the scandals, which saw political adviser James McGrath resign over accusations of racism and deputy mayor Ray Lewis quit after revelations about his past.

The mayor sought to draw a line under recent embarrassing episodes this week by announcing his intention to uphold and extend the London Living Wage, which goes beyond the national minimum wage. Johnson pledged to extend the new rate to those organisations funded by the London Development Agency and in hotels by the time the Olympic Games comes to London in 2012.