diff --git a/tools/bin/mbedtls-compare-merges b/tools/bin/mbedtls-compare-merges
new file mode 100755
index 00000000..db6ab5b6
--- /dev/null
+++ b/tools/bin/mbedtls-compare-merges
@@ -0,0 +1,114 @@
+#!/usr/bin/env python3
+"""Compare merges between two TF-PSA-Crypto or Mbed TLS branches.
+
+Invoke this script from a git checkout.
+"""
+
+import argparse
+import os
+import re
+import subprocess
+import sys
+from typing import Dict, Iterator, List, NamedTuple
+
+
+class MergedPR(NamedTuple):
+    sha: str
+    pull: int
+    description: str
+
+
+Options = argparse.Namespace
+
+
+def run_git(options: Options, cmd: List[str]) -> str:
+    """Run git and return the text output.
+
+    Remove newline or null terminators. Assume UTF-8 encoding.
+    """
+    raw = subprocess.check_output(['git'] + cmd,
+                                  cwd=options.directory,
+                                  encoding='utf-8')
+    return raw.rstrip('\0\n')
+
+
+def get_base(options: Options) -> str:
+    """Get the base commit (merge base of the reference branch and backport branch)."""
+    output = run_git(options,
+                     ['merge-base', options.backport_branch, options.reference_branch])
+    return output
+
+
+def parse_commit_info(info: str) -> MergedPR:
+    sha, subject, body = info.splitlines()
+    m = re.match(r'Merge pull request #([0-9]+)', subject)
+    pull = int(m.group(1))
+    description = re.sub(r'(\[backport[^][]*\]|\[[0-9.]+\]:? *|backport +[0-9.]+)\W', '', body, flags=re.I).strip()
+    return MergedPR(sha, pull, description)
+
+def get_merges(options: Options, base: str, head: str) -> List[MergedPR]:
+    """Get pull request merged on the given branch in the given interval."""
+    cmd = ['log', '--merges', '--grep=^Merge pull request ']
+    cmd += ['--format=%h\n%s\n%b', '-z']
+    if options.since:
+        cmd.append('--since=options.since')
+    cmd.append(base + '..' + head)
+    output = run_git(options, cmd)
+    commits = output.split('\0')
+    return [parse_commit_info(info) for info in commits]
+
+
+def missing_merges(dict1: Dict[str, MergedPR],
+                   dict2: Dict[str, MergedPR]) -> Iterator[MergedPR]:
+    """Find merges in the first list that are missing from the second list."""
+    for description, pr in dict1.items():
+        if description not in dict2:
+            yield pr
+
+def report_missing(title: str, pr_list: List[MergedPR]) -> None:
+    """Report the given pull requests.
+
+    Produce no output if the list is empty
+    """
+    if not pr_list:
+        return
+    print(title)
+    for pr in sorted(pr_list, key=lambda pr: pr.pull):
+        print(f'#{pr.pull}\t{pr.description}')
+
+def compare_merges(reference_list: List[MergedPR],
+                   backport_list: List[MergedPR]) -> None:
+    """Compare merges in the two list."""
+    reference_dict = {pr.description: pr for pr in reference_list}
+    backport_dict = {pr.description: pr for pr in backport_list}
+    not_backported = list(missing_merges(reference_dict, backport_dict))
+    report_missing('No backport:', not_backported)
+    backport_only = list(missing_merges(backport_dict, reference_dict))
+    report_missing('Only in LTS:', backport_only)
+
+
+def main(argv: List[str]) -> None:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument('--backport-branch', '-b',
+                        metavar='BRANCH',
+                        required=True,
+                        help='Backport branch')
+    parser.add_argument('--directory', '-C',
+                        metavar='DIR',
+                        default=os.curdir,
+                        help='Use this directory as the git worktree')
+    parser.add_argument('--reference-branch', '-a',
+                        metavar='BRANCH',
+                        default='development',
+                        help='Reference branch')
+    parser.add_argument('--since', '-s',
+                        metavar='DATE',
+                        help='Only consider commits since this date')
+    options = parser.parse_args()
+    base = get_base(options)
+    reference = get_merges(options, base, options.reference_branch)
+    backport = get_merges(options, base, options.backport_branch)
+    compare_merges(reference, backport)
+
+if __name__ == '__main__':
+    main(sys.argv[1:])