diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/FirDiagnosticsCollector.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/FirDiagnosticsCollector.kt
index 1c54834632d..95d4eb50d3c 100644
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/FirDiagnosticsCollector.kt
+++ b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/FirDiagnosticsCollector.kt
@@ -13,12 +13,4 @@ object FirDiagnosticsCollector {
         collector.registerAllComponents()
         return collector
     }
-
-    // Use in CLI compiler
-    @Suppress("unused")
-    fun createParallel(session: FirSession): AbstractDiagnosticCollector {
-        val collector = ParallelDiagnosticsCollector(session, numberOfThreads = 4)
-        collector.registerAllComponents()
-        return collector
-    }
 }
diff --git a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/ParallelDiagnosticsCollector.kt b/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/ParallelDiagnosticsCollector.kt
deleted file mode 100644
index 35c825b62e0..00000000000
--- a/compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/collectors/ParallelDiagnosticsCollector.kt
+++ /dev/null
@@ -1,77 +0,0 @@
-/*
- * Copyright 2010-2020 JetBrains s.r.o. and Kotlin Programming Language contributors.
- * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
- */
-
-package org.jetbrains.kotlin.fir.analysis.collectors
-
-import org.jetbrains.kotlin.fir.FirSession
-import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
-import org.jetbrains.kotlin.fir.analysis.diagnostics.FirDiagnostic
-import org.jetbrains.kotlin.fir.analysis.diagnostics.SimpleDiagnosticReporter
-import java.util.*
-import java.util.concurrent.Executors
-import java.util.concurrent.Future
-import java.util.concurrent.atomic.AtomicInteger
-
-class ParallelDiagnosticsCollector(session: FirSession, private val numberOfThreads: Int) : AbstractDiagnosticCollector(session) {
-    init {
-        require(numberOfThreads >= 1) {
-            "Number of threads should be at least 1"
-        }
-    }
-
-    private var reporters = initializeReporters()
-    private val collectorLocalIndex = ThreadLocal<Int>()
-    private val collectorIndexCounter = AtomicInteger()
-    private val futures = LinkedList<Future<*>>()
-
-    private val pool = Executors.newFixedThreadPool(numberOfThreads) { runnable ->
-        Thread {
-            collectorLocalIndex.set(collectorIndexCounter.getAndIncrement())
-            runnable.run()
-        }
-    }
-
-    private fun initializeReporters(): List<SimpleDiagnosticReporter> {
-        return (1..numberOfThreads).map { SimpleDiagnosticReporter() }
-    }
-
-    override fun initializeCollector() {
-        reporters = initializeReporters()
-        futures.clear()
-    }
-
-    override fun getCollectedDiagnostics(): Iterable<FirDiagnostic<*>> {
-        futures.forEach { it.get() }
-        return Iterable {
-            object : Iterator<FirDiagnostic<*>> {
-                private val globalIterator = reporters.iterator()
-                private var localIterator = globalIterator.next().diagnostics.iterator()
-
-                private fun update() {
-                    while (!localIterator.hasNext() && globalIterator.hasNext()) {
-                        localIterator = globalIterator.next().diagnostics.iterator()
-                    }
-                }
-
-                override fun hasNext(): Boolean {
-                    update()
-                    return localIterator.hasNext()
-                }
-
-                override fun next(): FirDiagnostic<*> {
-                    update()
-                    return localIterator.next()
-                }
-            }
-        }
-    }
-
-    override fun runCheck(block: (DiagnosticReporter) -> Unit) {
-        futures += pool.submit {
-            val reporter = reporters[collectorLocalIndex.get()]
-            block(reporter)
-        }
-    }
-}
\ No newline at end of file