The RMT union said that it was holding a strike ballot "in response to London Underground riding roughshod over agreements and abusing a range of agreed policies and procedures".
They are unhappy with plans to split a depot in Acton Town into two - claiming that that tube bosses are "ripping up rosters and booking times" and "refusing perfectly reasonable requests for decent staff facilities".
RMT General Secretary Bob Crow said:
"Driver and instructor members on the Piccadilly Line are furious at this unilateral attack by the company on working conditions, agreements and procedures and we are moving forwards with plans for a ballot for strike action.
"We will of course be in talks with our sister drivers union ASLEF and London Underground should be in no doubt about the unions determination to protect working conditions and to stop the abuse of procedures."
More top news
The mayoral candidate said he believed the spike in knife crime and the restrictions imposed on police to stop and search are linked.
Dragos Moisica raped the victim on her 12th birthday in a hotel in Kenton. He has been jailed for 12 years.
A week after the sinkhole appeared, it is unclear when the area will be declared safe.