Willis Towers Watson is suing Alliant for trying to “steal millions of dollars of revenues” after the West Coast broker poached a 12-strong construction team from its larger rival.

In a 25 July complaint filed against Alliant and one of its former employeed - Florida-based Brent Hartman - Willis accused its smaller rival of trying to “decimate” its construction practice at a “nationwide level”.

It is the latest suit filed in what is becoming an increasingly-acrimonious battle between the two firms over lucrative US construction business.

Last month, Willis sued Bill Noonan, the former boss of its North American construction division, after he defected to Alliant with at least nine of his colleagues and allegedly a significant amount of commercially sensitive information.

As part of the “destructive, premeditated corporate raid”, Willis said it was aware of another 15 senior and junior staff that were approached by Alliant.

Now, Willis has said the number of brokers headed for Alliant could be as high as 12 and has gone after the company itself, accusing Alliant of convincing its staff to breach their contracts.

In a complaint filed in Florida, Willis said: “Alliant is attempting to steal millions of dollars of revenues from Willis by convincing Willis employees to not honour their contractual obligations to Willis in their employment agreement.”

Willis attempted to convince the Florida district court to hand a temporary restraining order and preliminary injunction to Alliant that would have forced Hartman to abide by a 15-day notice period.

However, the court refused, finding that ambiguity in the executive’s employment contract “gravitates against the likelihood of success” at a full-blown trial.

Two weeks before Willis filed its most recent suit in Florida, Hartman and his former Willis colleague Danielle Maxey - who also moved to Alliant - lodged a preemptive complaint in Georgia, arguing that the dispute belonged there.

And last week, Alliant told the Florida court that a judge in Georgia had found that the restrictive covenants Willis was trying to get Hartman to adhere to were “unenforceable and void as a matter of law”.

In the order, the Georgia county court blocked Willis from trying to enforce the notice period or non-solicitation agreement against Hartman and Maxey. It also blocked Willis from trying to pursue the matter in a number of other cases and told the broker to stop its attempts to prevent the two brokers from taking up their roles at Alliant.

The course of the case has mirrored a similar dispute between Alliant and Aon in 2016 over its construction business. The similarities even extend to the language used in the complaint.

In that dispute, Aon alleged that Alliant “decimated” its San Jose office by luring over 27 of its brokers led by Michael Heffernan who headed up the unit and served as regional managing director of construction.

Then, Heffernan filed a preemptive action just hours after resigning in a suspected bid to anchor any litigation in California where restrictive covenants are less enforceable.

A similar tactic was also used in 2011, when Alliant took circa 60 employees from Aon’s West Coast construction team led by Peter Arkley.

Aon said that within three days of Arkley’s resignation it had lost more than 100 clients worth more than $20mn in revenues to Alliant.

A judge the said that a suit filed in California by Arkley - on the day that he and his team resigned - was an attempt to tie future legal proceedings to courts in the employee-friendly Golden State.

The case against Noonan, whose 20 July appointment at Alliant was announced at the same time as Hartman, is ongoing in a New York district court.

Neither Alliant nor Willis responded to a request for comment.