MPs have raised concerns that safety measures are taking more than a year to implement, blaming parliament’s spending watchdog, Ipsa, and security contractor for a “lottery” system.

Fears have grown about the protections offered to MPs after the killing of the Conservative backbencher Sir David Amess at a constituency surgery this month.

Despite receiving assurances over security assessments and equipment for their houses and offices, several MPs – all speaking anonymously – told the Guardian they have experienced long delays or inadequate equipment.

Panic alarms, known as “lone worker devices”, were said to falter. One MP in north-west England said that when they put it in their bag the “SOS” button was held down, which is supposed to trigger someone checking on their safety – but they never received any such contact. An MP in south-west England said they tested their device several times after Amess’s killing. “I thought given the heightened situation we ought to see what’s going on, and literally nothing happened.”

Fears have been expressed about insufficient protection for constituency offices. A Midlands MP said it had taken a year to fit security doors and the building alarm had occasionally shown errors in the middle of the night. A north-east MP said there were too many problems to document and his office door had to be fixed several times.

Whether work gets done quickly or not was branded a “lottery” by another, who said staff had to make daily or weekly calls to chase progress on security equipment being signed off by the Independent Parliamentary Standards Authority (Ipsa) watchdog or installed by Chubb, the outgoing parliamentary security contractor.

Even when work was completed, there were still complaints. A north-west England MP’s aide said that when security alterations were made to their main office door, they were told by the police that they were not adequate.

MPs’ homes give particular cause for concern as many list their address on election ballot papers. A London MP said it had taken 10 months for work to begin to improve security on their home. Before parliament switching security suppliers from Chubb to AD from 1 November, the MP said: “No one has shed a tear that Chubb have lost the contract. But the people who are in the middle of work or still waiting for work to begin … don’t want to have start from scratch with the new supplier.”

A Midlands MP said they faced a wait of five months for upgraded security at their home: “We requested it all and kept going back to Chubb and for five months they said: ‘We can’t do anything until Ipsa have signed off the budget.’ They’ve got the stuff, they’re ready to go, but until they’ve had confirmation that they’re going to get paid, they can’t do it.”

In another issue, a female MP wanted an alarm fitted at her home, but because it was listed, she was told this would require special planning permission, meaning her address would be published. Another MP said it was a “nightmare” that they heard had “affected quite a few people”.

One Tory was strongly critical of the delays, saying: “The fact that measures are only being completed now … is beyond a joke, it’s just not acceptable for it to have taken this long. As we’ve seen with the latest attacks on MPs and their offices … this is getting more and more serious, and I just don’t think Ipsa or Chubb take it as seriously as they should.”

Some MPs said they had experienced few difficulties and were understanding about “what is obviously going to be a logistical nightmare”, with an office manager praising a recent “brilliant” upgrade of security at their office.

Chubb said it was proud of its performance and “committed to delivering excellent service and have received positive feedback throughout this period”. A spokesperson added it would ensure a “smooth transition of services” to the new parliament security provider.

Ipsa said it funded “all measures recommended by the police” and stressed MPs’ security budgets are “uncapped and published in aggregate to ensure that there are no barriers to MPs receiving the security provisions they need”.

Explaining why all MPs who spoke to the Guardian wanted to remain anonymous, one said: “MPs really should not be discussing our security in this much detail, as we are constantly advised not to, for obvious reasons, from the day we arrive here.”

A parliament spokesperson said they took the security of MPs very seriously and all were “offered a range of security measures to ensure they are kept as safe as possible and are able to carry out their duties”, and added current arrangements are “kept under constant review”.