By Carl O'Donnell

(Reuters) - Alere Inc <ALR.N> alleges Abbott Laboratories <ABT.N> is trying to stymie its planned $5.8 billion takeover of the diagnostics company by purposefully delaying key submissions to anti-trust regulators, according to a lawsuit made public on Tuesday.

Alere claims in its complaint that Abbott has avoided responding to a second request by the Federal Trade Commission in a bout of "buyer's remorse" spurred by a desire to free up capital for Abbott's other major planned deal - a $24 billion acquisition of rival St. Jude Medical <STJ.N>.

Abbott denied the allegations, arguing that Alere's financial problems and related delays in filing its financial statements had slowed the deal's progress. Abbott also said it had been approached by a whistleblower who alleges that Alere is deliberately hiding information about its Indian operations.

"Alere’s complaint is nonsense and without merit," Abbott said in a statement. "Their description of events is fiction and nothing but a publicity stunt. Abbott is compliant with its obligations under the merger agreement."

Alere's planned deal with Abbott ran into trouble when it revealed that it was under investigation by the U.S. Department of Justice for some of its foreign sales practices and that it would not be able to provide certain key regulatory filings on time.

Prior to the deal, Alere already had revealed that its accounting practices had been under scrutiny by the Securities and Exchange Commission.

Abbott agreed to acquire Alere in February. In late April, Abbott struck an even bigger deal to buy St. Jude to position itself as the dominant player in the market for cardiovascular devices.

After the second deal was announced, Alere said in a filing that it had declined an offer from Abbott to pay it up to $50 million to break off their merger agreement.

Alere said last week that it had sued Abbott in Delaware Chancery Court but the complaint was only made public on Tuesday.

In its lawsuit, Alere said Abbott's chief executive officer, Miles White, said he would make life a "living hell" for everyone in Alere if it did not agree to walk away from the deal.

The suit claims that Abbott "inundated" Alere with about 175 document requests and asked for more than 40 interviews in an attempt to find evidence of a breach of its agreement.

It said Abbott's allegedly slow response to requests from anti-trust regulators was a fall-back attempt to prevent the deal from closing.

In a response to Alere's lawsuit filed Wednesday, Abbott said the timing of its response to regulators amounts to "a tactical disagreement among the parties about how to best secure antitrust clearance."

Abbott noted the current deal agreement does not expire for at least eight months and that a court intervention into its dealings with regulators at this stage would likely be unprecedented.

Abbott also said in its response to the lawsuit that it had received the tip from a whistleblower, who alleged that Alere had been obstructing its attempt to investigate possible legal violations by Alere in India by coaching witnesses to provide false information.

(Reporting by Carl O'Donnell; Editing by Michael Erman and Bill Trott)