- 6 updates
The Business Secretary Vince Cable has said that it is not sensible to deal with UKIP by "insulting" or "ignoring" them.
He told Sky News' Murnaghan programme: "I think it's very important that UKIP are subject to the kind of scrutiny that we are subjected to and other major parties.
"It's absolutely right, I have never believed that it's sensible to deal with Ukip by insulting them or ignoring them.
"They are a force at the moment and they should be subject to scrutiny and subject to debate, let's try and find out what their policies are, it isn't terribly clear."
It has emerged that police are investigating an allegation of postal vote fraud by UKIP
A Northumbria Police spokeswoman said officers are investigating a report of alleged electoral fraud in the Cowpen area of Blyth, Northumberland.
Detective Inspector David Brown said: "We can confirm that we have received a complaint of possible postal vote fraud in the Cowpen.
"We are in the early stages of the investigation and enquiries are ongoing."
Conservative Cabinet minister Ken Clarke has said that UKIP's politicians are "clowns" with no "positive" policies.
His comments came as the party accused the Tories of conducting a "morally reprehensible" smear campaign against its candidates in this week's local elections.
Speaking to Sky News' Murnaghan programme, he said: "It's very tempting to vote for a collection of clowns or indignant, angry people who promise that somehow they will allow you to take your revenge on the people who caused it.
"You should actually vote for people who you think are going to be sensible county councillors."
The Transport Secretary has said Ukip candidates are being put under the same scrutiny as those from other parties as the party accused the Tories of a smear campaign.
Patrick McLoughlin told BBC One's Andrew Marr Show. "Candidates are always put under scrutiny and I think it's right. Why should Ukip candidates get away without any scrutiny when other parties have scrutiny as far as their candidates are concerned?"
"I don't know anything about a smear campaign."
Asked whether it was right to trawl through would-be councillors' social media accounts, he said: "I don't know whether that's happened, I'm just saying it happens to all parties and candidates are put under scrutiny."
Godfrey Bloom, a senior UKIP MEP, has complained via a series of leaked emails that forging Ukip's policy platform is like "herding cats", insisting senior figures needed to learn to toe the line.
In a series of exchanges with Treasurer Stuart Wheeler, leaked to the Observer, Bloom warned that "some quite senior party members are going to have to stable their hobby horses".
"Having worked on the defence paper for over one year it would appear Ukip has more military and naval experts than we have soldiers," he wrote.
"Most of them do not agree with each other. It is like herding cats.
"We are also attracting new members who bring main party 'baggage'. Focus groups, quotas, even political correctness. We must be wary of listening to these siren voices. We did not get where we are today by following, but leading."
The MEP said he had been in talks with free market think-tanks including the Institute of Economic Affairs and Civitas, and suggested Ukip could buy their policies "off the shelf" where they are close to "our own small government, low tax, libertarian position".
UKIP has accused the Conservative party of running a "morally reprehensible" smear campaign by trawling through potential councillors' Twitter and Facebook posts.
The party - which is investigating a handful of candidates over links to groups such as the BNP and alleged racist and homophobic comments - said it did not condone "unpalatable views".
A spokesman insisted it would not bow to a "political lynch mob".
The row came as emails leaked to the Observer revealed that one of the party's MEPs is concerned about excessive "political correctness" among new recruits.