Pandya, 31, is the candidate for the UK Independence Party, which is opposed to Britain's membership of the European Union.
In 2010, the party polled 3.1 per cent of the votes, did not win any seat but was the fourth largest party in terms of the popular vote.
On his blog, Pandya called Islam "morally flawed and degenerate" and said he backed Geert Wilder, a controversial Dutch politician who allegedly called Islam a retarded ideology.
The byelection was caused by the resignation of Peter Soulsby of the Labour Party, who stood down from Parliament to contest the election for Mayor of Leicester.
He wrote: "A theological system that fundamentally encourages discrimination between those who believe it and those who don't, treating the latter as second-class citizens, is backward. A system that treats women as slaves without chains is morally flawed and degenerate."
"Cultural practices in many parts of the world which include child marriages and the death penalty for practising homosexuality are reminders that man is capable of going back to the dark ages very quickly."
He goes on to ask: "Why should Britain, the country that fathered the modern world, put up with this, as Wilder's put it, 'retarded ideology'.
"We do not need to ban the Koran as Wilder's suggests, but we do need to put such ideas to the sword through the vehicle of rational debate and exercise our legislative competence in Parliament to curb them."
Reports from Leiceter said that the city's Federation of Muslim Organisations (FMO) was surprised at Pandya's "hostile" comments, which it said were "cheap pot shots".
Pandya wrote: "Islamic culture inherently rejects the Western way of life, more specifically the Protestant work ethic that has successfully built the economies of the West.
"It is also fundamentally socially intolerant, closing itself off to the rest of society and local communities and forming ghettos that are economically dysfunctional and ethically espouse, perhaps without realising it, intolerance that undermines both social and human capital".
Suleman Nagdi, of the FMO, said: "I am surprised at the UKIP candidate taking such a hostile approach in his web blog by blaming the Muslim community for virtually every problem in society".
Nagdi said he was even more surprised because the candidate has not attended any meetings and has "instead hid behind his measly words".
"There are a number serious charges in the web blog against Muslims which the FMO would be very keen on having a public debate about. Rather than hiding behind words, we wish to engage in a constructive and mature debate about some of the important issues facing people in the UK today regardless of whether they are Muslim, Christian or from any other faith communities," he said.
"At a time when many people may lose their jobs or lose vital services, I would rather we focus on seeking solutions to these major challenges rather than taking cheap pot shots at one particular community."
Pandya's father migrated to England. He was born in Harrow, and read law at the University of Leicester, before taking his LLM with Distinction in International Law at the London School of Economics.