The film director and activist Ken Loach has claimed that his beloved home city of Bath is being ruined by unsympathetic developments designed to attract ever more visitors and argues that it is losing its sense of age and history.

Loach, who has lived in Bath since the 1970s, suggested that if the trend continues it could lose its Unesco world heritage status.

“Bath was dusty and a little shabby when we moved here,” Loach said. “It did look its age and you felt its history in its streets and buildings and little alleyways. The sense of the past was palpable. There were some bad modern buildings but there was a patina of age.

“The problem now is that it has been sharpened up for the tourists. It’s too clean. It’s like an old person with Botox. You don’t get the same sense of the past. It’s too clean, too sharp.”

Loach is giving a public lecture on Friday night at the Assembly Rooms in Bath – one of the city’s Georgian gems – as part of the Festival of the Future City Bath.

Speaking to the Guardian before the event, Loach said successive local councils had tried to maximise income from tourism but this had led to developments that put in danger the very thing people came to Bath for – its glorious history and splendid architecture.

Loach called for planners to try to “preserve the city in a minimal way rather than try to make big architectural statements”, adding: “It’s like when you are restoring a picture – you do the minimum you have to just to keep the picture intact and make sense of it. That should be the approach.”

But market forces were leading to short-sighted over-development, he said. “The market is very destructive. It will say we want lots more hotels because there is a demand. But if you build the new hotels, you’ll kill the demand because the hotels spoil the reason people are coming.”

Developments that Loach is particularly concerned about include the Georgian-style SouthGate shopping centre, which opened in 2009. He is also worried over schemes to build new student accommodation and the possibility of building a new rugby stadium on the Rec in the city centre, which he calls “grotesque”.

“There’s too much imitation Georgian architecture,” he said. “Most cities are eclectic. There’s a bit of medieval, Georgian, some Victorian and some 20th century. That’s fine. Bath is different because it was built within 100 years or less. It has a homogeneity. You spoil that if you have an eclectic mix. You eat away at the homogeneity. You need to preserve the city in a minimal way rather than try to make big architectural statements.”

Loach worries that unless the focus is changed, the city risks losing its Unesco world heritage site status. The UN body praises Bath’s “quality of architecture and urban design, its visual homogeneity and its beauty” but it adds: “The main pressures currently facing the site are large-scale development and the need for improved transport.”

Bath has drawn visitors since it was founded by the Romans 2,000 years ago. There are now about 5 million daytrippers to Bath and north-east Somerset a year and 1m overnight visits. About 10,000 people are employed in the tourism sector.

But Loach argues that the city had become too obsessed with attracting tourists: “It feels like the city centre is too geared to visitors.”

He regrets the loss of smaller shops such as ironmongers, chemists, greengrocers. “You don’t need endless scented candles. Those things aren’t on your shopping list if you live here. We need to re-evaluate what the city needs if it is continue to be a place to cherish and find a way of helping people live here in a sustainable way. Tourism should come way down the priorities.”

Loach is also concerned that houses are becoming unaffordable to local people. “There is poverty and gross inequality. House prices have skyrocketed so that local people can’t afford them.”

But Loach said he still liked living in the city. “It’s still a lovely place to live. We’ve got friends here, brought up children here.” And he could not contemplate living far away from his football club, Bath FC, where he argues you find the real people of Bath.

“If you go and stand on the terrace you’ll hear the wit and wisdom of the people of Bath. It’s warm and welcoming and friendly. Nobody cares who you are as long as you are a good supporter.”

The Festival of the Future City Bath runs until Saturday evening. At 4pm on Saturday an event called The people’s debate: what makes great architecture? will be held at The Edge, University of Bath. Admission is free.