Mobile phone companies should allow customers to roam between networks in areas of the UK where they struggle to get reception, a group of MPs has said.
The British Infrastructure Group said foreign visitors get better coverage, as they are not tied to any provider, so can use the strongest signal.
The report said 17 million customers had poor reception at home and it named 525 areas with non-existent coverage.
Phone companies insist they are working hard to make their coverage better.
Roaming allows customers' phones to connect to another operator's network if their own service provider is not available in a particular area.
The cross-party group of about 90 backbench MPs called on ministers to make sweeping changes, including changing the law to allow domestic roaming in the UK, making it cheaper for customers to switch provider and identifying the worst phone networks.
The report said mobile phone coverage in the UK had not improved significantly since 2014 when the government agreed a £5bn investment deal with the network operators.
The agreement is expected to fall short of its target of providing coverage to 90% of the UK's geographical area by the end of 2017.
Group chairman Grant Shapps said: "It is unacceptable that areas in Britain continue to have such poor mobile connectivity, and that overseas visitors can expect better mobile coverage than Britons stuck with a single provider.
"The time for excuses from the mobile sector is over. The government must make a better call for Britain and bring national mobile coverage policy into the 21st Century."
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Gary MacRae, who runs the Hazel Bank Country House Hotel in Borrowdale, Cumbria, said he had to rely on a landline because there was no mobile reception at the premises.
He told BBC Radio 5 live: "The only way our guests are able to get signal is either go to the top of one of the small mountains just along from us that you can see from our window or drive down the road five or six miles."
Mr MacRae said in previous years the lack of mobile signal would have been a selling point but now people want it to stay connected to their loved ones.
He also said a mobile phone signal was needed in the area "just in case of emergencies" for those who may get into trouble while out walking in the countryside.
A workaround for customers?
MP Grant Shapps told the BBC he used a foreign SIM during election campaigning, which allowed him to connect to whichever network had the strongest signal.
Money Saving Expert's Martin Lewis said in most cases using a foreign SIM, or a global roaming SIM, in an unlocked handset would allow customers to receive better overall network coverage.
He suggested the most effective way would be to have a dual SIM phone which would mainly use a UK SIM but could switch to a foreign SIM when there was no signal.
But he said the cost would be likely to be higher as customers would be paying increased roaming charges for making and receiving calls.
Mr Lewis, who previously wrote a blog on the issue, said: "It would be a very expensive way to make calls in the UK.
"But you could do it if it was absolutely integral to you. If you are the type of person who would use a satellite phone then doing this would not be a bad solution.
"It's going to cost a fortune compared to using a normal phone. On that basis it's not a practical solution for most people."
Mobile UK, the trade association for mobile phone companies, said allowing customers to roam between networks would not provide the "right incentives" for operators to make future investments.
Spokesman Hamish MacLeod said: "This was looked at by the government a couple of years ago and it was decided that the cost of doing it would not be justified, it's technically difficult to do in a localised way, and that it wouldn't always offer the best customer experience.
"But the most important thing was that it would not have the right incentives in place for network investments to be made."
Large exit fees
Mr MacLeod told the BBC the industry was working hard to hit its target of providing 90% coverage and investment was being put in place to limit reception blackspots.
However, he said domestic roaming would not provide an incentive for companies to build "the right infrastructure", such as expensive towers in remote areas, if the service then had to be shared with other operators.
The report also stated that customers were at risk of being hit with large exit fees if they decide to terminate their contract, even if it was due to poor quality service.
The government said a bill going through Parliament would give regulator Ofcom the power to fine firms that do not deliver improvements.