The incident occurred between junction 10 at Wisley and junction 11, Chertsey and it is causing long tailbacks of up to seven miles. It comes as Britain prepares for strikes in public transport that are expected to take place tomorrow, Tuesday, and on Thursday and Saturday this week.
Two of the four lanes were closed between junctions J9 and J10 on the carriageway until the incident is cleared.
An update from traffic service Inrix read: “Long delays and queueing traffic for seven miles due to earlier broken down car on M25 clockwise between J9 A243 (Leatherhead) and J10 A3 (Wisley Interchange). Travel time is 30 minutes.”
Congestion was reported from Wisley Interchange and St Peters Way, Chertsey, until Cobham Services.
Traffic England said that the event would clear by 8.30am.
One of the lanes was also closed on the M25 clockwise between junctions J5 and J6.
All of the lanes were opened at around 8am but delays remained.
The strikes by the Rail, Maritime and Transport union (RMT) expected to start tomorrow are likely to keep half of Britain’s rail lines closed.
Transport for London (TfL) has “strongly encouraged” people not to travel on London Underground on June 21 because of a 24-hour walkout by the RMT and Unite.
Chief secretary to the Treasury Simon Clarke has apologised for the “misery” the rail strike will cause and denied that the Government is actively looking for a fight with unions.
He told BBC Breakfast: “We absolutely don’t want them to go ahead, I recognise this is going to cause misery for millions of people and I am profoundly sorry about that.
“No-one is suggesting there’s some kind of pay freeze required here, we all want to see a sensible pay increase.
“Linked to that we need to see reform of some of the practices that make our railway a very unsustainable entity at the moment.”
He called for a “sustainable” rail industry, saying the way the network operates is “not fit for the 2020s”.
Asked about the demands for pay increases by union members, Mr Clarke told Kay Burley on Sky News: “Public-sector pay discipline really matters here.
“We have an inflation problem in this country … if we don’t want that problem to either intensify or prolong itself, then we need to be sensible around pay awards.
“If we give awards which are above inflation in this landscape, then we are in a really difficult place in terms of bringing down inflation, which in turn obviously is driving the cost of living.”