The start of a month-long strike has brought an even more arduous rush hour for hundreds of thousands of commuters on South Western Railway, one of Britain’s biggest train operators.

Passengers were forced to queue outside some stations while others crammed on to overcrowded trains, as barely half of SWR’s normal services ran.

The first of 27 days of strikes by the RMT union over the role of guards on trains came on a morning of freezing temperatures, while technical problems caused further delays to the heavily reduced timetable.

Passengers struggled to board some of early services, as commuters departed earlier to maximise their chances on a network that normally serves around 600,000 trips daily between London Waterloo and counties including Surrey and Hampshire.

Commuters who found seats described “horrendous” journeys. Richard Clarke, from Farncombe, on a delayed 7.01am train to Waterloo, said: “I am on the 7.01 and it is horrendous, full and standing … No one could even force their way on once we arrived at Woking.”

Passengers expressed anger as SWR laid on shorter trains than usual. Clare Moriarty, permanent secretary at Brexit department DexEU, tweeted the train operator: “I cannot believe that on a strike day when there only two trains from my station in the peak hour you have *shortened* train length by a third. Please have some thought for your passengers.”

Within Greater London, where passengers were held outside busy stations such as Earlsfield, local bus services were quickly filled and not stopping as people sought alternatives.

RMT, Rail, Maritime and Transport Union workers protest outside Waterloo. Photograph: Alberto Pezzali/AP

Compounding the delays, a track circuit failure affected services between Reading and Ascot on Monday morning, and a safety issue with some rolling stock meant shorter trains were operating on some routes.

Neither the train operator nor the union gave any indication that the strikes, due to last until the end of the month, could be called off. Talks to resolve the long-running row about the future role of guards on trains broke down on Friday.

The RMT said its members were “rock solid and united” at the start of the strike. The general secretary, Mick Cash, said the union was “angry and frustrated that a set of proposals that would have guaranteed the safety-critical role of the guard at the point of despatch, and which would have cost the company absolutely nothing, were kicked back in our faces last week.”

SWR had yet to comment on Monday but earlier accused the RMT of “moving the goalposts” and being “intent on striking no matter what”.

Business groups criticised the strike. Sean McKee, director of policy and public affairs for London Chamber of Commerce, said: “It’s sadly inevitable that this cynically long strike will have an impact on commuting workers and businesses during peak commuting times. With trains due to finish earlier, it will also impact shift work and the night-time economy – key to the festive economy.”

Labour’s shadow transport secretary, Andy McDonald, backed the striking railway workers and said South Western Railways need to “give their heads a shake”. He told LBC: “If they would do what the other train operators have done and give that guarantee and put those guards on the trains, this matter would be resolved imminently and people could go about their preparations for Christmas without any interruption whatsoever.”

South Western has become the focal point now in the long-running dispute over guards and driver-controlled operation of trains. Walkouts first contributed to a year of commuter misery at Southern, while the row has spread to Northern, Merseyrail and now also West Midlands, where RMT members are walking out each Saturday until 2020.

While South Western has pledged to keep a second staff member onboard trains, the RMT has sought firmer guarantees about their role.